Fast Lithium Ion Transport Research Articles

Highly Ionic Conductive and Degradable Solid Electrolyte Enabled by a Three-Dimensional Cross-Linking Copolymeric Structure

High ionic conductivity is an essential prerequisite for the application of solid electrolyte (SE) oriented toward solid-state lithium battery (SSLB). Meanwhile, sustainability and environment friendliness of solid electrolytes are required from the green chemistry perspective. However, research on solid electrolytes with simultaneously high ionic conductivity and good degradability remains in its infancy. Herein, a degradable network copolymer solid electrolyte (DNCPSE) was designed and prepared for simultaneously realizing fast lithium-ion transport with a high ionic conductivity of 7.5 × 10–4 S cm–1 at room temperature and fast degradable properties (e.g., completely degraded within 1.5 h in alkaline condition). Experimental characterizations have demonstrated that the construction of a copolymeric network with sufficient polar groups not only boosts fast lithium-ion hopping but also facilitates the whole decomposition of DNCPSE. By virtue of the combined features, this DNCPSE presents remarkable degradable and electrochemical performances. As a result, the DNCPSE-based Li symmetrical cells display high stability (e.g., >1200 h at 0.1 mA cm–2). Moreover, the Li|DNCPSE|LiFePO4 full cells also display impressive cycling performance (e.g., >200 cycles at 1C). This work provides a promising designed rationale and strategy for sustainable solid electrolytes toward green and efficient solid-state lithium battery.

Functional Separator Enabled by Covalent Organic Frameworks for High-Performance Li Metal Batteries.

Uncontrolled ion transport and susceptible SEI films are the key factors that induce lithium dendrite growth, which hinders the development of lithium metal batteries (LMBs). Herein, a TpPa-2SO3 H covalent organic framework (COF) nanosheet adhered cellulose nanofibers (CNF) on the polypropylene separator (COF@PP) is successfully designed as a battery separator to respond to the aforementioned issues. The COF@PP displays dual-functional characteristics with the aligned nanochannels and abundant functional groups of COFs, which can simultaneously modulate ion transport and SEI film components to build robust lithium metal anodes. The Li//COF@PP//Li symmetric cell exhibits stable cycling over 800h with low ion diffusion activation energy and fast lithium ion transport kinetics, which effectively suppresses the dendrite growth and improves the stability of Li+ plating/stripping. Moreover, The LiFePO4//Li cells with COF@PP separator deliver a high discharge capacity of 109.6 mAh g-1 even at a high current density of 3 C. And it exhibits excellent cycle stability and high capacity retention due to the robust LiF-rich SEI film induced by COFs. This COFs-based dual-functional separator promotes the practical application of lithium metal batteries.

CuO-ZnO submicroflakes with nanolayered Al2O3 coatings as high performance anode materials in lithium-ion batteries

Transition metal oxides are said to have the ability to enhance the gravimetric capacity of lithium-ion batteries by two or three times that of current state-of-the-art graphite anodes. Recent reports have demonstrated that the combined utilization of structural architecture and surface modification is an attractive strategy to improve lithium storage capability. In this study, novel CuO-ZnO@Al2O3 submicroflakes were prepared by magnetron sputtering deposition of Cu-Zn alloy films on a removable sacrificial substrate, followed by a facile thermal oxidation treatment and Al2O3 coating procedure by particle atomic layer deposition. They combine the advantages of CuO-ZnO submicroflakes, such as high lithium storage capability and fast lithium ion transportation, and Al2O3 nano-coating with effective protection of the electrode interface during cycling. When utilized as anode materials for LIBs, the CuO-ZnO@Al2O3 submicroflakes exhibit superior specific capacity, enhanced cycling stability, and outstanding rate capability compared with pristine CuO-ZnO submicroflakes, commercial CuO and ZnO powders. The CuO-ZnO@Al2O3 submicroflakes electrodes deliver a high reversible capacity of 814 mAh g−1 at a current density of 50 mA g−1, and still maintain a moderate capacity of 447 mAh g−1 at a high current density of 1000 mA g−1. Pairing with a commercial LiFePO4 cathode, full cell shows high capacity retention and stable cycling performance, suggesting the feasibility of the CuO-ZnO@Al2O3 submicroflakes in practical energy storage applications. In addition, our findings also provide a clear proof-of-concept of the surface coating technique, which might be applied widely to other materials and devices where nano-coating produces desirable properties.

A Safer High-Energy Lithium-Ion Capacitor Using Fast-Charging and Stable ω-Li3 V2 O5 Anode.

Lithium-ion capacitors (LICs) are flourishing toward high energy density and high safety, which depend significantly on the performance of the intercalation-type anodes used in LICs. However, commercially available graphite and Li4 Ti5 O12 anodes in LICs suffer from inferior electrochemical performance and safety risks due to limited rate capability, energy density, thermal decomposition, and gassing issues. Here a safer high-energy LIC based on a fast-charging ω-Li3 V2 O5 (ω-LVO) anode with a stable bulk/interface structure is reported. The electrochemical performance, thermal safety, and gassing behavior of the ω-LVO-based LIC device are investigated, followed by the exploration of the stability of the ω-LVO anode. The ω-LVO anode exhibits fast lithium-ion transport kinetics at room/elevated temperatures. Paired with an active carbon (AC) cathode, the AC||ω-LVO LIC with high energy density and long-term endurability is achieved. The accelerating rate calorimetry, in situ gas assessment, and ultrasonic scanning imaging technologies further verify the high safety of the as-fabricated LIC device. Theoretical and experimental results unveil that the high safety originates from the high structure/interface stability of the ω-LVO anode. This work provides important insights into electrochemical/thermochemical behaviors of ω-LVO-based anodes within LICs and offers new opportunities to develop safer high-energy LIC devices.

Sandwich Structured Metal oxide/Reduced Graphene Oxide/Metal Oxide-Based Polymer Electrolyte Enables Continuous Inorganic-Organic Interphase for Fast Lithium-Ion Transportation.

Introducing inorganic fillers into organic poly(ethylene oxide)(PEO)-based electrolyte has attracted substantial attention to enhance its ionic conductivity and mechanical strength, but limited inorganic-organic interphasesare always caused by isolated particles agglomeration. Herein, a variety of sandwich structured metal oxide/reduced graphene oxide(rGO)/metal oxide nanocomposites to optimize lithium-ion conduction by interconnected amorphous organic-inorganic interphases in lithium metal batteries, are proposed. With the support of high surface area rGO, the agglomeration of metal oxide particles is precluded, forming continuous amorphous organic-inorganic interphases with stacked layer-by-layer structure, thus creating 3D interconnected lithium-ion transportation channels vertically and laterally. Besides, metal oxide nanoparticles with hydroxyls possess high affinity toward bis(tri-fluoromethanesulfonyl)imideanionsby hydrogen bindings between hydroxyls and fluorine and metal-oxygen bonds, releasing more free lithium ions. Consequently, PEO-ZnO/rGO/ZnO electrolyte delivers superior ionic conductivity of 1.02 × 10-4 S cm-1 at 25°C and lithium-ion transference number of 0.38 at 60°C. Furthermore, ZnO/rGO/ZnO insertion promotes the formation of LiF-rich stable solid electrolyte interface, endowing Li symmetric cells with long-term cycling stability over 900 hours. The corresponding LiFePO4 cathode possesses a high reversible specific capacity of 130 mAh g-1 at 0.5C after cycling 300 cycles with a poor capacity fading of 0.05% per cycle.

TaCl5-glassified Ultrafast Lithium Ion-conductive Halide Electrolytes for High-performance All-solid-state Lithium Batteries

For all-solid-state batteries (ASSBs), high ionic conductivity of solid-state electrolyte (SSE) and its good physical contact with the cathode is vital to realize very efficient ion transport inside the cathode layer. In this work, our team introduce a halide glass lithium solid electrolyte LiTaCl6 with ultrahigh ionic conductivity over 10 mS/cm at 25 °C. It is interesting that TaCl5 is able to glassify many simple lithium salts (LiF, LiCl, LiBr, LiI, Li2O, LiOH, Li2O2 and Li2S) and results in a series of glass-phase super lithium-ion conductors (Xn− = F−, Cl−, Br−, I−, O2−, OH−, O2−, S2−) with high room-temperature ionic conductivities ranging from 4.37 to 10.95 mS/cm. Their properties of no grain boundary and fast lithium-ion transport enable ASSBs using a high nickel cathode (LiNi0.91Co0.06Mn0.03O2) with 98.3% capacity retention after long-term 2,000 cycles (4.3 V versus Li+/Li, 1.34 mAh/cm2, 2C rate). Most importantly, -based ASSBs have: 1. excellent electrochemical performance in an ASSB with ultra-high loading over 7 mAh/cm2, 2. ultra-high potential window up to 4.8 V and 92.81% capacity retention after 200 cycles. These results provide new insights in synthesizing halide-based glass SSE and suggest a new approach for realizing ASSB with high voltage and large loading.

Phosphonate-Functionalized Ionic Liquid Gel Polymer Electrolyte with High Safety for Dendrite-Free Lithium Metal Batteries.

The conventional lithium-ion battery technology relies on the liquid carbonate-based electrolyte solution, which causes excessive side reactions, serious risk of electrolyte leakage, high flammability, and significant safety hazards. In this work, phosphonate-functionalized imidazolium ionic liquid (PFIL) is synthesized and used as a gel polymer electrolyte (GPE) to replace the organic carbonate-based electrolyte solution. The as-prepared ionic liquid-based gel polymer electrolyte (IL-GPE) shows low crystallinity, flame retardance, and excellent electrochemical performance. Thanks to the fast double channel transport of lithium ions in the IL-GPE electrolyte, a high ionic conductivity of 0.48 mS cm-1 and a lithium-ion transference number of 0.37 are exhibited. Symmetrical lithium cells with IL-GPE retain stable cycling even after 3000 h under 0.1 mA cm-2. IL-GPE exhibits good compatibility toward lithium metal, yielding excellent long-term electrochemical kinetic stability. IL-GPE induces the formation of a uniform and robust SEI layer, inhibiting the growth of lithium dendrites and improving the rate performance and cycle stability. Furthermore, Li/LiFePO4 cells exhibit a specific capacity of 63 mA h g-1 after 150 cycles at 5.0 C, with a capacity retention of 90.2%. It is foreseen that this GPE is a promising candidate to enhance the safety of high-performance lithium metal batteries.

Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur (Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice. One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide (CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and −50 °C. The synthesized laminar CC-rGO composite is mixed with acetylene black (AB) and coated on a commercial polypropylene (PP) membrane, resulting in a separator (CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Rational design and low-cost fabrication of multifunctional separators enabling high sulfur utilization in long-life lithium-sulfur batteries

The lithium-sulfur (Li-S) battery with an ultrahigh theoretical energy density has emerged as a promising rechargeable battery system. However, the practical applications of Li-S batteries are severely plagued by the sluggish reaction kinetics of sulfur species and notorious shuttling of soluble lithium polysulfides (LiPSs) intermediates that result in low sulfur utilization. The introduction of functional layers on separators has been considered as an effective strategy to improve the sulfur utilization in Li-S batteries by achieving effective regulation of LiPSs. Herein, a promising self-assembly strategy is proposed to achieve the low-cost fabrication of hollow and hierarchically porous Fe3O4 nanospheres (p-Fe3O4-NSs) assembled by numerous extremely-small primary nanocrystals as building blocks. The rationally-designed p-Fe3O4-NSs are utilized as a multifunctional layer on the separator with highly efficient trapping and conversion features toward LiPSs. Results demonstrate that the nanostructured p-Fe3O4-NSs provide chemical adsorption toward LiPSs and kinetically promote the mutual transformation between LiPSs and Li2S2/Li2S during cycling, thus inhibiting the LiPSs shuttling and boosting the redox reaction kinetics via a chemisorption-catalytic conversion mechanism. The enhanced wettability of the p-Fe3O4-NSs-based separator with the electrolyte enables fast transportation of lithium ions. Benefitting from these alluring properties, the functionalized separator with p-Fe3O4-NSs endows the battery with an admirable rate performance of 877 mAh g−1 at 2 C, an ultra-durable cycling performance of up to 2176 cycles at 1 C, and a promising areal capacity of 4.55 mAh cm−2 under high-sulfur-loading and lean-electrolyte conditions (4.29 mg cm−2, electrolyte/ratio: 8 µl mg−1). This study will offer fresh insights on the rational design and low-cost fabrication of multifunctional separator to strengthen electrochemical reaction kinetics by regulating LiPSs conversion for developing efficient and long-life Li-S batteries.

Atomistic Investigation of Solid Electrolyte Interphase: nanostructure, Chemical Composition and Mechanical Properties

Using lithium metal as the anode is a promising way to raise the energy density of batteries, but inevitable lithium dendrite growth hinders the development of this kind of batteries. Albeit great efforts were devoted to uncovering the mystery of the solid electrolyte interphase (SEI), which determines the stability of the plating and stripping of lithium metal, our understanding of SEI at the atomic scale is limited due to its complex structure and composition. This work proposes a computational framework, based on the reactive force field molecular dynamics (ReaxFF), for simulating the SEI formation. Our results suggest the SEI in the standard EC/DEC electrolyte resembles a heterogeneous mosaic structure with inorganic crystalline grains randomly dispersed within the amorphous polymer matrix, as the consequence of the bottom-up growth sequence. When lithium nitrate is present in the electrolyte, the preferential reduction of lithium nitrate effectively regulates the electrolyte decomposition for rendering a bilayer structure with the lithium nitrate reduction products, Li3N and LiNxOy, on top of the amorphous polymer matrix. Although these N-containing compounds are good lithium-ion conducting materials for retaining a uniform, fast lithium-ion transport through the SEI, we observe a significant decrease in the mechanical performance due to the high-porosity structure.

Novel In Situ Growth of ZIF-8 in Porous Epoxy Matrix for Mechanically Robust Composite Electrolyte of High-Performance, Long-Life Lithium Metal Batteries.

Polymer electrolytes (PEs) with high flexibility, low cost, and excellent interface compatibility have been considered as an ideal substitute for traditional liquid electrolytes for high safety lithium metal batteries (LMBs). Nevertheless, the mechanical strength of PEs is generally poor to prevent the growth of lithium dendrites during the charge/discharge process, which seriously restricts their wide practical applications. Herein, a mechanical robust ZIF-8/epoxy composite electrolyte with unique pore structure was prepared, which effectively inhibited the growth of lithium dendrites. Meanwhile, the in situ growth of ZIF-8 in porous epoxy matrix can promote the uniform flux and fast transport of lithium ions. Ultimately, the optimal electrolyte shows high ionic conductivity (2.2 × 10-3 S cm-1), wide electrochemical window (5 V), and a large Li+ transference number (0.70) at room temperature. The Li||NCM811 cell using the optimal electrolyte exhibits high capacity and excellent cycling performance (83.2% capacity retention with 172.1 mA h g-1 capacity retained after 200 cycles at 0.2 C). These results indicate that the ZIF-8/epoxy composite electrolyte is of great promise for the application in LMBs.

A Multi-Phase Niobium Oxide Electrode for High-Power Lithium-Ion Batteries

Niobium oxide-based materials are promising anodes for high-power lithium-ion batteries. The electrochemical performance of these oxides depends sensitively on the crystal and the defect structures. For example, a recent study revealed that the planar defects introduced to the H-phase of Nb2O5 shear structure greatly enhanced the rate capability and structural durability. Our recent study indicates that the M-phase with a tetragonal crystal structure displayed the highest electrochemical performance among all crystalline phases of Nb2O5 studied, due likely to its fast transport of lithium ions and electrons through the ‘block structures’. In this presentation, we will report our findings in the development of a composite electrode composed of a tetragonal and a monoclinic phase of niobium pentoxide with desired defect structures (denoted as d-H,M-Nb2O5), synthesized using a solvothermal process followed by annealing under controlled conditions. Microscopic analysis reveals that the d-H,M-Nb2O5 has NbO6 and NbO4 block structures of both the M-Nb2O5 and the H-Nb2O5. The electrode based on the d-H,M-Nb2O5 exhibits the highest rate capability (142 mAh g-1 at 20 A g-1) and excellent cycling stability (86% capacity retention after 2000 cycles at 6 A g-1) among recently reported niobium pentoxides. Further, detailed crystallographic and defect structures, the physicochemical characteristics, and the long-term cycling behavior will be discussed.

Metal-organic framework (MOF)-incorporated polymeric electrolyte realizing fast lithium-ion transportation with high Li+ transference number for solid-state batteries.

Composite polymer electrolytes (CPEs) show significant advantages in developing solid-state batteries due to their high flexibility and easy processability. In CPEs, solid fillers play a considerable effect on electrochemical performances. Recently, metal-organic frameworks (MOFs) are emerging as new solid fillers and show great promise to regulate ion migration. Herein, by using a Co-based MOF, a high-performance CPE is initially prepared and studied. Benefiting from the sufficient interactions and pore confinement from MOF, the obtained CPE shows both high ionic conductivity and a high Li+ transference number (0.41). The MOF-incorporated CPE then enables a uniform Li deposition and stable interfacial condition. Accordingly, the as-assembled solid batteries demonstrate a high reversible capacity and good cycling performance. This work verifies the practicability of MOFs as solid fillers to produce advanced CPEs, presenting their promising prospect for practical application.

Application of transition metal boride nanosheet as sulfur host in high loading Li-S batteries

Two-dimensional (2D) metal boride material (MBene) has aroused concern recently. However, the research and application exploration for MBene materials with more exposure sites are seriously restricted due to lack of suitable preparation methods. Herein, a kind of composites of monolayer MBene nanosheets and carbon nanotube (mono-MBene/CNT) is prepared through ice template method for the first time and applicated as a novel cathode host in high-loading lithium-sulfur (Li-S) batteries. Benefiting from multifunctional advantages of mono-MBene/CNT cathode including anchoring lithium polysulfides (LiPS), multiple functional sites and fast lithium-ion transport, the cells with S@mono-MBene/CNT cathode exhibit superior long-term cycling performance over 1000 cycles. Most notably, even if the sulfur loading is up to 15.28 mg cm−2, the cells with S@mono-MBene/CNT cathode deliver an initial area capacity of 12.73 mAh cm−2 and the capacity can also maintain at 11.07 mAh cm−2 after 120 cycles (86.96 % capacity retention) with current density of 21.80 mA cm−2, which is approximately 3 times higher than the capacity of commercial lithium-ion batteries. This work not only provides a guiding role in preparing monolayer MBene material, but also exhibits the application prospect for MBene material in the fields of energy storage.

Solution-Processable Redox-Active Polymers of Intrinsic Microporosity for Electrochemical Energy Storage.

Redox-active organic materials have emerged as promising alternatives to conventional inorganic electrode materials in electrochemical devices for energy storage. However, the deployment of redox-active organic materials in practical lithium-ion battery devices is hindered by their undesired solubility in electrolyte solvents, sluggish charge transfer and mass transport, as well as processing complexity. Here, we report a new molecular engineering approach to prepare redox-active polymers of intrinsic microporosity (PIMs) that possess an open network of subnanometer pores and abundant accessible carbonyl-based redox sites for fast lithium-ion transport and storage. Redox-active PIMs can be solution-processed into thin films and polymer–carbon composites with a homogeneously dispersed microstructure while remaining insoluble in electrolyte solvents. Solution-processed redox-active PIM electrodes demonstrate improved cycling performance in lithium-ion batteries with no apparent capacity decay. Redox-active PIMs with combined properties of intrinsic microporosity, reversible redox activity, and solution processability may have broad utility in a variety of electrochemical devices for energy storage, sensors, and electronic applications.

Two-dimensional montmorillonite-based heterostructure for high-rate and long-life lithium-sulfur batteries

In lithium-sulfur batteries, the polysulfide redox reaction kinetics is obstructed by unfavorable electron conduction and ion transportation. To address this issue, a two-dimensional (2D) heterostructure with fast ion/electron transport bi-pathways is designed herein by well integrating monolayer lithium-montmorillonite (MMT) and nitrogen-doped reduced graphene oxide (RGO). The low diffusion barrier on the Li-MMT contributes to the fast lithium ion transport, and the nearby RGO builds high electron conduction network, which enables high-efficiency adsorption-diffusion-conversion for polysulfides and achieves fast electrochemical reaction kinetics. Consequently, the lithium-sulfur batteries using the heterostructure interlayer show effective suppression towards the notorious “shuttle effect” of polysulfides, as well as deliver high initial specific capacity of 1317 mAh g−1 at 0.2 C, high rate capability of 848 mAh g−1 even at 3 C, and low capacity decay rate of 0.011% per cycle at 1 C over 200 cycles and 0.067% per cycle at 2 C over 600 cycles. The corresponding pouch cell shows high initial discharge capacity of 1542 mAh g−1 at 0.05 C. This work exhibits the potential application of the low-cost and environmentally-friendly clay as the 2D heterostructure interlayer material for realizing high-energy-density, long-lasting, and high-rate Li-S batteries.

High-Rate Solid Polymer Electrolyte Based Flexible All-Solid-State Lithium Metal Batteries.

A flexible poly(vinylidene fluoride)-polyetherimide@poly(ethylene glycol) (PVDF-PEI@PEG) solid composite polymer electrolyte is prepared by an in situ thermal curing approach. The homogeneous PVDF-PEI composite porous membrane with an optimized PVDF and PEI weight ratio increases the amorphous phase, while the fast lithium ion transport channels are formed through the filled PEG electrolytes. The optimized polymer electrolyte exhibits high ionic conductivity of 2.36 × 10-4 S cm-1 at 60 °C and lithium ion transference number of 0.578 as well as excellent electrochemical stability window of 5.5 V. Moreover, the superior stability toward lithium metal anode enables over 3600 h cycling of the Li//Li symmetric cell at 0.1 mA cm-2. In particular, the LiFePO4//Li battery delivers high specific capacities of 132.4 and 111.5 mAh g-1 with a retention of 86.6% and 85.9% after 200 cycles at 2 C and 100 cycles at 3 C rate under 60 °C, respectively, demonstrating the feasibility as an energy storage device with high rate capability.

Optimization of Loading Content of Li4Ti5O12-Hard Carbon Composite Anode for the Fast Charging Li-Ion Battery

Fast charge of lithium-ion batteries (LIBs) needs anode and cathode materials operating at high current densities. Li4Ti5O12 (LTO) can enable fast lithium ion (Li+) transport due to its 3D crystal structure. Nonetheless, this material suffers from low specific capacity and high operating voltage. In contrast, Hard Carbon (H.C) with high specific capacity and low practical voltage is one of the promising anode materials for high-energy lithium-ion batteries. However, practical application of this material is compromised with its slow kinetic, and reduced cycling performance associated with irreversibly trapped ions in its structure [1]. In this report, effect of loading ratio of H.C and LTO composite anode on the electrochemical behavior of fast charging lithium ion battery is studied. Electrochemical characterization results show that a certain loading of H.C plays a critical role in improving the electrochemical performance of LTO-H.C composite electrodes. Specifically, superior cycling stability and specific capacity achieved for the composite electrode with 20 wt.% H.C. It is believed that composite electrodes with an optimized ratio can effectively contribute to Li-ion storage and form a robust protective solid electrolyte interface (SEI) on the electrode surface. The latter might minimize further electrolyte decomposition and continuous growth of the SEI layer upon cycling, then improves the cycling stability of the electrode. In addition, the cycling performance and rate capability of LiNiMnCoO2 (NMC) with different nickel (Ni) and manganese (Mn) contents were evaluated and compared. The results clearly suggest that higher Ni content can improve specific capacity (115 mAhg-1for NMC333 vs 149 mAhg-1 for NMC811 at 1C). However, cycling stability deteriorates with increasing the Ni content (77% capacity retention for NMC333 vs 45% for NMC811 after 300 cycles). It is postulated that electrodes with higher Ni content are susceptible to transition metal dissolution and side reactions at electrode-electrolyte interface, which could lead to performance degradation by impeding Li+ diffusion across the electrode, and irreversible consumption of Li+ [2]. Finally, the possibility of use of the optimized anode for fabricating full cell with the selected NMC cathode is investigated.

Understanding of the Electrochemical Behavior of Lithium at Bilayer-Patched Epitaxial Graphene/4H-SiC.

Novel two-dimensional materials (2DMs) with balanced electrical conductivity and lithium (Li) storage capacity are desirable for next-generation rechargeable batteries as they may serve as high-performance anodes, improving output battery characteristics. Gaining an advanced understanding of the electrochemical behavior of lithium at the electrode surface and the changes in interior structure of 2DM-based electrodes caused by lithiation is a key component in the long-term process of the implementation of new electrodes into to a realistic device. Here, we showcase the advantages of bilayer-patched epitaxial graphene on 4H-SiC (0001) as a possible anode material in lithium-ion batteries. The presence of bilayer graphene patches is beneficial for the overall lithiation process because it results in enhanced quantum capacitance of the electrode and provides extra intercalation paths. By performing cyclic voltammetry and chronoamperometry measurements, we shed light on the redox behavior of lithium at the bilayer-patched epitaxial graphene electrode and find that the early-stage growth of lithium is governed by the instantaneous nucleation mechanism. The results also demonstrate the fast lithium-ion transport (~4.7–5.6 × 10−7 cm2∙s−1) to the bilayer-patched epitaxial graphene electrode. Raman measurements complemented by in-depth statistical analysis and density functional theory calculations enable us to comprehend the lithiation effect on the properties of bilayer-patched epitaxial graphene and ascribe the lithium intercalation-induced Raman G peak splitting to the disparity between graphene layers. The current results are helpful for further advancement of the design of graphene-based electrodes with targeted performance.

Low-Temperature Synthesis of a Porous High-Entropy Transition-Metal Oxide as an Anode for High-Performance Lithium-Ion Batteries.

Transition-metal oxides (TMOs) are promising anode materials for high-performance lithium-ion batteries (LIBs) because of their abundant reserves and high theoretical capacity. However, the poor conductivity, unstable solid electrolyte interface (SEI) film, and poor cycling stability still limit their practical applications. As a novel kind of anode material, a high-entropy oxide (HEO) is a single-phase crystal structure composed of multiple metal elements, demonstrating a huge potential for energy storage applications due to the synergistic effect of various metal species. Herein, we have designed the porous spinel-phase HEO (Cr0.2Fe0.2Co0.2Ni0.2Zn0.2)3O4 synthesized at low temperature by a sol-gel method. On the one hand, the unique porous nanostructure not only promotes transport of the electrolyte but also alleviates the volume change of active materials upon cycling. On the other hand, the stabilization effect of entropy can suppress the formation of cation short-range order within the crystalline structure of HEO by a lattice distortion effect, thus guaranteeing a fast lithium-ion transport and achieving an excellent electrochemical performance. As a result, the as-prepared HEO-450 electrode delivers 1022 mAh/g after 1000 cycles at 1 A/g and 220 mAh/g at an ultrahigh current density of 30 A/g, respectively.