Full-cell Assembly Research Articles

Scalable Synthesis of Bulk TiO2 Hybrids and Its Li-Storage Properties in “Rocking-Chair” Type Full-Cell Assembly with LiNi0.5Mn1.5O4 Cathode

TiO2 as an anode material in lithium-ion batteries (LIB) has abolished hurdles like irreversibility, cycling stability, rate capability, and energy density, which are vital for electrochemical performance. Conventionally, time-consuming and complex techniques like solvothermal methods are employed to synthesize TiO2. We herein open a new avenue towards a simple, scalable, and eco-friendly synthesis of bulk TiO2 anatase/bronze hybrids from sodium meta-titanate through a facile mechano-chemical and ion-exchange process under different temperature conditions (400, 450, and 500 °C). Structural and morphological features are analyzed through various characterization techniques such as XRD, FE-SEM, HR-TEM, and XPS. The bronze phase’s high reversibility, low redox potential, high current rate performance, and high power capability of the anatase phase make the hybrid attractive for fabricating high power and high energy density Li-ion power packs. The Li insertion/extraction properties are studied in half-cell assembly (Li/TiO2), where all three TiO2 hybrids exhibited promising results with an initial discharge capacity >165 mAh g-1 at a current rate of 0.05 A g-1 along with a capacity retention >90% after 100 cycles. A “rocking-chair” type full-cell configuration with high voltage LiNi0.5Mn1.5O4 cathode is fabricated, in which LNMO/TiO2-400 °C displayed a discharge capacity of ~88 mAh g-1 at a current rate of 0.05 A g-1. Moreover, the full cell exhibited a capacity retention of >70% after 100 cycles with a maximum energy density of 192.75 Wh kg-1. Figure 1

La-doped O3-type layered oxide cathode with enhanced cycle stability for sodium-ion batteries

Despite the considerable potential of O3-type layered oxide cathodes in sodium-ion batteries due to their high theoretical capacities, the rapid capacity degradation caused by high Na+ diffusion barriers and irreversible phase transitions seriously hampers their practical application. Herein, we propose the La-doping strategy in O3-type layered oxide to decrease diffusion barriers and strengthen transition metal–oxygen (TM-O) bonds, thereby significantly improving the electrochemical performance. The strong La-O bonding facilitates highly reversible O3-P3 phase transitions during (de)sodiation and enhances the stability of lattice oxygen at high voltages. Specifically, the La-doped O3-type oxide exhibits impressive cycling stability, with the capacity retention increasing from 63 % to 80 % after 500 cycles at 1C. The full cell assembly with La-doped oxide as cathode and hard carbon as anode demonstrates a high energy density of 323.7 Wh kg−1 at 0.1C, with a capacity retention of 74.6 % after 300 cycles at 1C. This work provides new insights in La-doping to promote the commercial application of O3-type cathodes for sodium ion batteries.

Mechanically Exfoliated Graphite for Highly Reversible Na-Storage with Carbon Coated Na3V2(PO4)3 Cathode with Low-Temperature Conditions.

Tremendous efforts are put forward to develop novel high-performance electrodes for Na-ion batteries (SIBs) in order to replace commercial Li-ion batteries (LIBs). Graphite, the most versatile anode for LIBs, fails to accommodate Na+ions owing to the poor thermodynamic stability of the binary graphite intercalation compound. This study aims to exfoliate the layers of graphite through a simple mechanical process at different time intervals (1, 5, 10, 20, 40, and 80h) and examine the potential candidate for Na-storage in the presence of carbonate-based electrolytes. This study reports that ball milling plays a vital role in the performance of the graphite in Na-storage. The graphite exfoliated for 80h (EG-80h) rendered an excellent reversible capacity of 209mAhg-1 with coulombic efficiency of >99% after 100 cycles in EC-based electrolyte. In situ impedance analysis is performed to validate the charge storage mechanism and Na-ion kinetics. The performance of EG-80h in a full-cell assembly is evaluated with a carbon-coated Na3V2(PO4)3 cathode, which exhibited an initial capacity of ≈75mAhg-1 andenergy density of 201Whkg-1. In addition, the adaptability of the NVPC/EG-80h cell at different temperatures is examined from -10 to 50°C, displaying excellent performance in both high and low-temperature conditions.

Superior electrochemical performance of metal ligand framework-neodymium oxide composite for energy storage devices

Battery supercapacitor hybrids are gaining increasing importance in the realm of energy storage, driven by their exceptional electrochemical attributes, where the choice of electrode material emerges as a paramount factor for their efficacy. Here the enhancement in the electrochemical activity from the synergistic effect produced by combining copper benzene tetra carboxylate with neodymium oxide (Cu-1,3,5-BTC/Nd2O3) along with the individual samples Cu-1,3,5-BTC, and Nd2O3, is studied via various electrochemical measurements which includes CV, GCD and EIS in half cell assembly and for real-world applications in full cell assembly. The hybrid device achieved a specific capacity (Qs) of 390 C/g with an energy density (Es) of 91 Wh/kg and power density (Ps) of 5950 W/kg respectively. Semi-empirical approaches such as linear and quadratic models were further employed and compared to scrutinize the CV curves and to deconvolute the capacitive and diffusive contribution.

Thermal stability analysis of nitrile additives in LiFSI for lithium-ion batteries: An accelerating rate calorimetry study

Although lithium-ion batteries (LIBs) are extensively used as secondary storage energy devices, they also pose a significant fire and explosion hazard. Subsequently, thermal stability studies for LiPF6- and LiFSI-type electrolytes have been conducted extensively. However, the thermal characteristics of these electrolytes with thermally stable additives in a full cell assembly have yet to be explored. This study presents a comprehensive accelerating rate calorimetry (ARC) study. First, 1.2-Ah cells were prepared using a control commercial LiPF6 electrolyte and LiFSI with a specific succinonitrile additive and ethyl-methyl carbonate as a thermally stable electrolyte additive. The kinetic parameters involved in heat generation and their effects on the thermal properties of the ARC module were analyzed from the heat-wait-seek (HWS), self-heating (SH), and thermal runaway (TR) stages. The results indicate that the addition of a succinonitrile additive to the LiFSI electrolyte lowers the decomposition temperatures of the solid electrolyte interface (SEI) owing to polymerization with Li at the anode, while simultaneously increasing the activation energy of reaction temperatures at SEI between the separator and the electrolyte. The maximum thermal-runaway temperature decreased from 417 °C (ΔH = 5.26 kJ) (LiPF6) to 285 °C (ΔH = 2.068 kJ) (LiFSI + succinonitrile). This study provides key insights to the thermal characteristics of LiPF6 and LiFSI during the self-heating and thermal runaway stages and indicates a practical method for achieving thermally stable LIBs.

Functional AlF3 modification over 5 V spinel LiCoMnO4 cathode for Li-ion batteries

We report the improved electrochemical activity of the 5 V LiCoMnO4 (LCMO) cathode with the functionalization of AlF3 coating. LCMO@AlF3 is prepared by adopting the co-precipitation technique followed by a wet coating by altering the concentration of AlF3 by 1–3 wt.%. LCMO@AlF3 exhibits improvement in the electrochemical performance compared to pristine LCMO. In addition, LCMO@AlF3 exhibits superior electrochemical performance with specific capacities of 107, 102, and 95 mAh g−1 and retentions of 68, 77, and 74% after 100 cycles for 1, 2, and 3 wt.% AlF3 coating. However, pristine LCMO shows a specific capacity of 105 mAh g−1 with a retention of 48% after 100 cycles. Also, LCMO@AlF3 exhibits a decrement in the irreversible capacity loss (ICL) compared to pristine LCMO, which enhances the coulombic efficiency of the former compared to the latter. Further, the AlF3 coating of 2 and 3 wt.% has been optimized to exhibit excellent electrochemical performance. The diffusion coefficients are calculated from cyclic voltammetric and electrochemical impedance spectroscopic techniques and are in the order of ∼10−12 cm2 s−1. Further, in-operando and in-situ impedance studies are conducted to authenticate the electrochemical activity observed in half-cell studies. In full-cell assembly with Li4Ti5O12 (LTO) anode, the LCMO@AlF3: 2–3 wt.% exhibits better electrochemical performance compared to its bare configuration. In addition, the electrochemical activity at various temperature (−10 to 25 °C) conditions is performed and reported.

Synergistic Performance Boosts of Dopamine-Derived Carbon Shell Over Bi-metallic Sulfide: A Promising Advancement for High-Performance Lithium-Ion Battery Anodes.

A CoMoS composite is synthesized to combine the benefits of cobalt and molybdenum sulfides as an anodic material for advanced lithium-ion batteries (LIBs). The synthesis is accomplished using a simple two-step hydrothermal method and the resulting CoMoS nanocomposites are subsequently encapsulated in a carbonized polydopamine shell. The synthesis procedure exploited the self-polymerization ability of dopamine to create nitrogen-doped carbon-coated cobalt molybdenum sulfide, denoted as CoMoS@NC. Notably, the de-lithiation capacity of CoMoS and CoMoS@NC is 420 and 709 mAh g⁻1, respectively, even after 100 lithiation/de-lithiation cycles at a current density of 200mA g⁻1. Furthermore, excellent capacity retention ability is observed for CoMoS@NC as it withstood 600 consecutive lithiation/de-lithiation cycles with 94% capacity retention. Moreover, a LIB full-cell assembly incorporating the CoMoS@NC anode and an NMC-532 cathode is subjected to comprehensive electrochemical and practical tests to evaluate the performance of the anode. In addition, the density functional theory showcases the increased lithium adsorption for CoMoS@NC, supporting the experimental findings. Hence, the use of dopamine as a nitrogen-doped carbon shell enhanced the performance of the CoMoS nanocomposites in experimental and theoretical tests, positioning the material as a strong candidate for LIB anode.

Mo-MXene-filled gel polymer electrolyte for high-performance quasi-solid-state zinc metal batteries

The production of MXenes from the MAX phase typically requires hydrofluoric acid etching, a process with significant toxicity and severe environmental implications. Given the wide-ranging applications of MXenes, developing a large-scale, environmentally benign chemical etching process is highly desirable. The goal of this study was to establish selective electrochemical aluminum etching (E-etching) from the Mo3AlC2 MAX phase using an innovative 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (EMITFSI) and zinc trifluoromethane sulfonate (Zn(OTF)2) battery electrolyte formulation. The E-etching technique effectively removes the “A” layer from the Mo3AlC2 MAX phase at 60 °C using a TFSI−-based electrolyte. This method demonstrates that the resulting MXene terminal (Tx) contains O and OH groups. Subsequently, the resulting Mo2CTx MXene was embedded into a gel polymer electrolyte (GPE) as an inorganic filler. The Mo2CTx/EMITFSI/Zn(OTF)2/poly(vinylidene fluoride-co-hexafluoropropylene) (PVHF) GPE membrane displayed excellent ionic conductivity, Zn2+ transference number, and galvanostatic Zn plating/stripping compatibility with Zn anodes. Finally, the performance of a zinc-metal battery using a belt-like CaV6O16⋅3H2O cathode was evaluated as a full-cell assembly of CaV6O16⋅3H2O//Mo2CTx/EMITFSI/Zn(OTF)2/PVHF//Zn. This assembly showcased an impressive capacity of 155 mA h g−1, excellent durability (99%), coulombic efficiency approaching 100%, and excellent self-life over 200 h.

Conversion of toxic waste to wealth: Diesel soot carbon electrode for sodium-hybrid capacitor

In recent years, hybrid capacitors have proven to be an efficient technology in storing energy faster and at a higher energy capacity while utilizing a renewable source. Herein, we report diesel soot derived from automobile exhausts as a carbon source for all carbon sodium-ion hybrid capacitors. To achieve this, a simple synthesis method was used, followed by activation to significantly increase its charge storing capabilities. The high porosity of this activated diesel soot carbon allows us to achieve high charge storage capacity both as anode and cathode, while increased graphitization with interlayer expansion by heat-treatment technique allows us to obtain greater rate performance combined with superior cycle stability. As a result, activated diesel soot carbon could earn double the capacity as compared to pure diesel soot carbon with specific capacities of 198 and 78 mAhg−1 as anode and cathode, respectively. Full-cell assembly as a hybrid capacitor with carbon as both cathode and anode could deliver a maximum energy density of 97 Whkg−1 and a maximum power density of 10,000 Wkg−1 with cycle stability for 50,000 cycles. This article emphasizes the waste-to-wealth technique in active materials for energy storage devices more extensively.

An integrated study on the ionic migration across the nano lithium lanthanum titanate (LLTO) and lithium iron phosphate-carbon (LFP-C) interface in all-solid-state Li-ion batteries

A major challenge for the development of all-solid-state lithium-ion batteries (ASS-LIBs) relay on the development of an ideal electrolyte material and solving the interfacial issues at the electrode-electrolyte interface. Nano-crystalline lithium lanthanum titanate (LLTO) and lithium iron phosphate-carbon (LFP/C) has been prepared as electrolyte and cathode material for a solid-state lithium ion cell (LIBs). Prepared lithium lanthanum titanate, lithium iron phosphate-carbon and the composite powders were subjected to structural, optical, morphological and electrochemical characterizations. The high ionic conductivity of lithium lanthanum titanate (1.06 × 10−4), carbon coated lithium iron phosphate (5.01 × 10−5) and their interface (6.00 × 10−5) designate the pertinence of their full cell configurations. The full cell assembly has been characterized electrochemically to evaluate the performance of the interface. The assembled ASSBs show cyclability up to 55 initial cycles, with the nano-LLTO/LFP-C interface. The line scan analysis has been performed to identify the cation movement and accumulation of ions towards and across the cathode-electrolyte interface after cycling. The present study provides new direction and methodology for the detailed interface analysis across the nano-electrode- nano-solid electrolyte layer in all solid-state assemblies.

Effects of Excessive Prelithiation on Full-Cell Performance of Li-Ion Batteries with a Hard-Carbon/Nanosized-Si Composite Anode

The effects of excessive prelithiation on the full-cell performance of Li-ion batteries (LIBs) with a hard-carbon/nanosized-Si (HC/N-Si) composite anode were investigated; HC and N-Si simply mixed at mass ratios of 9:1 and 8:2 were analyzed. CR2032-type half- and full-cells were assembled to evaluate the electrochemical LIB anode behavior. The galvanostatic measurements of half-cell configurations revealed that the composite anode with an 8:2 HC/N-Si mass ratio exhibited a high capacity (531 mAh g−1) at 0.1 C and superior current-rate dependence (rate performance) at 0.1–10 C. To evaluate the practical LIB anode performance, the optimally performing composite anode was used in the full cell. Prior to full-cell assembly, the composite anodes were prelithiated via electrochemical Li doping at different cutoff anodic specific capacities (200–600 mAh g−1). The composite anode was paired with a LiNi0.5Co0.2Mn0.3O2 cathode to construct full-cells, the performance of which was evaluated by conducting sequential rate and cycling performance tests. Prelithiation affected only the cycling performance, without affecting the rate performance. Excellent capacity retention was observed in the full-cells with prelithiation conducted at cutoff anodic specific capacities greater than or equal to 500 mAh g−1.

Fluorine substitution enabled superior performance of NaxMn2-xO1.5F0.5 (x = 1.05–1.3) type Na-rich cathode

Among the various sodium cathodes, the potential of Na-rich layered oxides is yet to be fully utilized. Unlike their Li counterparts, they are least explored and are at least a generation behind in development. Addressing the same, herein, Na-rich NaxMn2-xO1.5F0.5 (x = 1.05–1.3) type cathodes were synthesized successfully and analyzed as potential electrodes for Na-ion battery applications. Oxygen loss in Na-based transition metal oxides is a common issue, and it is effectively addressed by fluorine substitution. In contrast to exploring a particular stoichiometry as in other Na-deficient layered cathodes, herein, Na-content was gradually increased from 1.05 to 1.3. The cathodes were synthesized using a conventional solid-state approach and quenched to achieve high crystallinity. Compounds with different sodium stoichiometry were electrochemically tested in a half-cell configuration. Among these compounds, the Na1.2Mn0.8O1.5F0.5 electrode exhibited very high capacities of 178 and 122 mAhg−1 at current densities of 10 and 1000 mA g−1, respectively. The Na-rich Na1.2Mn0.8O1.5F0.5 cathode was systematically analyzed to understand the mechanism underlying its superior performance using various structural and electrochemical analyses. Furthermore, to demonstrate its practicality, the Na-rich Na1.2Mn0.8O1.5F0.5 cathode was coupled with a hard carbon and Na-In alloy anode in a full-cell assembly.

A high-performance room-temperature magnesium ion battery with self-healing liquid alloy anode mediated with a bifunctional intermetallic compound

Liquid metals with a self-healing property can address the passivation issue of Mg metal and the huge volume variation problem of solid alloy-type anodes in rechargeable magnesium ion batteries (MIBs). Liquid Ga-based anodes show great potentials in MIBs, however, being operated at room temperature is a great challenge. Herein, a novel strategy is proposed to enhance the room-temperature Mg storage performance of liquid eutectic GaSn (EGaSn) alloy through constructing a bifunctional intermetallic compound (Ag3Ga) layer on the current collector. This Ag3Ga layer could greatly improve the wettability of EGaSn on the substrate in the electrolyte environment. Moreover, operando X-ray diffraction confirms that Ag3Ga could participate the reversible alloying/dealloying reactions during the discharge/charge processes and thus provide an extra capacity. Eventually, the Ag3Ga-mediated EGaSn anode exhibits outstanding electrochemical performance towards Mg storage in both half and full cells at room temperature (∼24 and 21 °C), as benchmarked with state-of-the-art anodes in MIBs. Specially, the MIBs could be stably cycled up to 600 cycles in the half cell configuration, and 100 cycles in the full cell assembly. This work provides useful information on the development of advanced anodes for MIBs.

V2O5vs. LiFePO4: Who is performing better in the 3.4 V class category? A performance evaluation in “Rocking-chair” configuration with graphite anode

Vanadium pentoxide (V2O5) brings vast interest in the promising host materials for the intercalation of multivalent ions, owing to its abundance in the earth crust, synthesizing facile methodologies, and offers maximum discharge capacity of >300 mAh g−1. However, V2O5 undergoes different phase transformations upon the intake of beyond 1 mol Li. Here, we report a comparative study of two versatile cathode materials, such as V2O5 (limiting 1 mol. Li) and LiFePO4. A solvothermal method is adopted to synthesize both two, and three-dimensional crystalline phases of V2O5 and LiFePO4, respectively. The spherical-shaped V2O5 exhibits the initial discharge capacity of 136 mAh g−1 in the half-cell assembly and renders stable cycle life. Subsequently, V2O5 is paired with the electrochemically lithiated graphite (LiC6) anode in full-cell assembly (V2O5/LiC6) and offers a maximum energy density of ∼266.7 Wh kg−1 (based on total mass loading). On the other hand, LiFePO4 also exhibits ∼136 mAh g−1 in the half-cell performance with stable cycle life. The full-cell LiFePO4/C delivers an energy density of ∼234.8 Wh kg−1. This clearly encourages that V2O5 is a strong contender for the 3.4 V class Li-ion cells and paves the new avenue for further exploration of advanced battery technologies.

Machine learning technique-based data-driven model of exploring effects of electrolyte additives on LiNi0.6Mn0.2Co0.2O2/graphite cell

Recently, state-of-the-art and perspective Li-ion batteries have been focused on NMC622 cathode for energy densities and power densities enhancement. This work introduces a novel approach of combining experimental data generation and computational power for understanding the effects of electrolyte additives including vinylene carbonate (VC), lithium bis(oxalate) borate (LiBOB), and fluoroethylene carbonate (FEC) in the carbonate-based electrolyte (a mixture of EC: EMC = 3:7), which caused on NMC622/graphite cell. Furthermore, a screening study of negative to the positive ratio (N/P ratio) confirmed that the best capacity matching of N/P ∼ 1.07 was taken for full-cell assembly. It was demonstrated that the presence of additives improved only initial capacity but suppress remarkably capacity fading. With 1 %wt. FEC, the cell delivered 155.1 mAh g−1 and remained 47.9% of initial capacity after 100 cycles compared to 140.5 mAh g−1 concentration and 9.3% after 30 cycles, respectively. However, using high FEC as a co-solvent of carbonate-based electrolyte is to be promising in improving long-cycling performance, even in a dual-additive electrolyte with LiBOB. To understand the additive's impact on cell performance, a simulation of an artificial neural network (ANN) was applied. Based on the ANN simulation, the cell could obtain 160 mAh g−1 and 65% capacity retention after 100 cycles when using 1.1 M LiPF6 in FEC: EC: EMC (0.7: 2.8:6.5) (%v) with 0.6 %wt. LiBOB and 0.01 %wt. VC. Therefore, the robust prediction of the technique for diagnostics and prognostics of LIBs is effective since it helps reduce experiment cost and save the time of conducting experiments.

Advantageous Tubular Structure of Biomass-Derived Carbon for High-Performance Sodium Storage

Biomass-derived carbon (BDC) is viewed as one of the most promising anode candidates for sodium-ion batteries (SIBs) owing to its natural abundance, low cost, and sustainability. However, fabrication of BDC with a preferred microstructure and morphology for high-performance sodium storage still remains a dilemma. Herein, we report using natural parasol fluff as a biomass precursor to highlight the significant role of the tubular structure for achieving high electrochemical performances with BDC. Different from high-temperature pyrolysis (over 1000 °C) commonly used for BDC, the interconnected porous carbon framework with a well-maintained tubular structure was prepared in a mild calcination temperature of 500 °C with the aid of KOH activation and Co2+-assisted graphitization. The as-prepared material with a large interlayer spacing (0.405 nm) and abundant self-doping heteroatoms demonstrates its excellent performance as the anode of SIBs by delivering a reversible capacity of 359.0 mA h g–1 at 30 mA g–1. Impressively, its full-cell capacity reaches 257.2 mA h g–1 at 30 mA g–1, which is among the highest values for carbon-based full-cell assembly. In addition to offering a potential industrializable BDC choice, this work highlights the significance of the tubular structure and provides tactics for screening of biomass precursors as well as the design of high-performance carbonaceous materials.

Highly Perforated V2 O5 Cathode with Restricted Lithiation toward Building "Rocking-Chair" Type Cell with Graphite Anode Recovered from Spent Li-Ion Batteries.

Current research motivation on fabricating next-generation lithium-ion batteries by averting the growing demand for battery raw materials brings enormous interest on the V2 O5 cathode again as a result of its abundance, ease synthesis, and tunable Li-intercalation properties. So far, the research activities are mainly focused on V2 O5 to attain a maximum capacity (>300 mAh g-1 ) for more than 1 mol. Li-intercalation which results in poor structural stability. Keeping this issue in mind, here, the full-cell assembly by limiting 1 mol is proposed and constructed. Li-insertion in V2 O5 as a cathode and LiC6 as an anode for the first time. Prior to the full-cell assembly, hydrothermally prepared rod-like V2 O5 reveals the specific capacity of 143 mAh g-1 in half-cell configuration with good cycling stability. The full-cell, V2 O5 /LiC6, offers a specific capacity of ≈236 mAh g-1 with a maximum energy density of ≈197.1Wh kg-1 . Furthermore, the practical feasibility of the cell has been examined at different temperatures that divulged a maximum energy density of 136Wh kg-1 at 50 °C. Also, the obtained results encourage V2 O5 as a strong contender for the commercial LiFePO4 /C system andpave the new directions for advanced battery technology.

Impact of carbonate-based electrolytes on the electrochemical activity of carbon-coated Na3V2(PO4)2F3 cathode in full-cell assembly with hard carbon anode

An immense effort has been put into developing high-performance electrodes to commercialize sodium-ion batteries, but research on developing an efficient electrolyte is lacking. This study aims to find the best carbonate-based electrolyte systems by incorporating the existing ideas reported in this field. The sodium superionic conductor (NASICON) type Na3V2(PO4)2F3-C (NVPF-C) was chosen as a cathode, and its compatibility with four different carbonate-based electrolyte solutions was studied in the half-cell assembly. Additionally, full-cell assembly with hard carbon as an anode is also explored. Binary and ternary combinations of the solvents ethylene carbonate, propylene carbonate, and dimethyl carbonate were employed with and without fluoroethylene carbonate as an additive. A systematic study was performed, including the in-situ impedance technique, and to determine the compatibility. Detailed galvanostatic studies for NVPF-C based half-cells, as well as hard carbon/NVPF-C full-cells, are performed, which shows that 1 M NaClO4 in propylene carbonate:dimethyl carbonate + fluoroethylene carbonate is a better electrolyte composition for this assembly. Subsequently, a temperature study was carried out on this electrolyte to test its performance.

Controlled Prelithiation of SnO2/C Nanocomposite Anodes for Building Full Lithium-Ion Batteries.

SnO2 is an attractive anodic material for advanced lithium-ion batteries (LIBs). However, its low electronic conductivity and large volume change in lithiation/delithiation lead to a poor rate/cycling performance. Moreover, the initial Coulombic efficiencies (CEs) of SnO2 anodes are usually too low to build practical full LIBs. Herein, a two-step hydrothermal synthesis and pyrolysis method is used to prepare a SnO2/C nanocomposite, in which aggregated SnO2 nanosheets and a carbon network are well-interpenetrated with each other. The SnO2/C nanocomposite exhibits a good rate/cycling performance in half-cell tests but still shows a low initial CE of 45%. To overcome this shortage and realize its application in a full-cell assembly, the SnO2/C anode is controllably prelithiated by the lithium-biphenyl reagent and then coupled with a LiCoO2 cathode. The resulting full LIB displays a high capacity of over 98 mAh g-1LCO in 300 cycles at 1 C rate.

Towards Improving the Practical Energy Density of Li-Ion Batteries: Optimization and Evaluation of Silicon:Graphite Composites in Full Cells

Increasing the energy density of Li-ion batteries is very crucial for the success of electric vehicles, grid-scale energy storage, and next-generation consumer electronics. One popular approach is to incrementally increase the capacity of the graphite anode by integrating silicon into composites with capacities between 500 and 1000 mAh/g as a transient and practical alternative to the more-challenging, silicon-only anodes. In this work, we have calculated the percentage of improvement in the capacity of silicon:graphite composites and their impact on energy density of Li-ion full cell. We have used the Design of Experiment method to optimize composites using data from half cells, and it is found that 16% improvements in practical energy density of Li-ion full cells can be achieved using 15 to 25 wt% of silicon. However, full-cell assembly and testing of these composites using LiNi0.5Mn0.5Co0.5O2 cathode have proven to be challenging and composites with no more than 10 wt% silicon were tested giving 63% capacity retention of 95 mAh/g at only 50 cycles. The work demonstrates that introducing even the smallest amount of silicon into graphite anodes is still a challenge and to overcome that improvements to the different components of the Li-ion battery are required.