Superior High-rate Capability Research Articles

Inducing and Understanding Pseudocapacitive Behavior in an Electrophoretically Deposited Lithium Iron Phosphate Li-Metal Battery as an Electrochemical Test Platform.

Our study has effectively employed electrophoretic deposition (EPD) using AC voltage to develop a lithium iron phosphate (LFP) Li-ion battery featuring pseudocapacitive properties and improved high C-rate performance. This method has significantly improved the battery's specific capacity, achieving an impressive 100 mAhg-1 at a 5 C discharge rate, which showcases its superior high-rate capability. Additionally, the battery displayed excellent reversibility during its performance cycles. These results confirm the EPD method's efficacy in improving LFP electrode performance, yielding notable improvements in cycling stability and high-rate capability. The enhanced capacity and high-rate performance of the electrophoretic-deposited LFP electrodes are largely due to the fast kinetics facilitated by pseudocapacitive behavior-induced charge storage and a high Li-ion diffusion constant measured in our EPD-deposited LFP electrodes. This underscores the practicality of our approach and the development of a fundamental test platform to investigate the pseudocapacitive charge storage mechanism in electrodes with typical battery-like behavior.

Boosting the high-rate performance of lithium-ion battery anodes using MnCo2O4/Co3O4 nanocomposite interfaces.

Herein, a mesoporous MnCo2O4/Co3O4 nanocomposite was fabricated using a polyvinylpyrrolidone (PVP)-assisted hydrothermal synthesis method by maintaining only the non-stoichiometric ratio of Mn and Co (2 : 6), leading to an extra phase of Co3O4 coupled with MnCo2O4. Microstructural analysis showed that the obtained sample has a uniform nanowire-like morphology composed of interconnected nanoparticles. The stoichiometric ratio (2 : 4) was maintained to synthesize pure MnCo2O4 for comparative analysis. However, the obtained structure of pure MnCo2O4 was found to be irregular and fragile. After their employment as anode-active materials, the nanocomposite electrode showed superior high rate capability (1043.8 mA h g-1 at 5C) and long-term cycling stability (773.6 mA h g-1 after 500 cycles at 0.5C) in comparison to the pure MnCo2O4 electrode (771.5 mA h g-1 at 5C and 638.9 mA h g-1 at 0.5C after 500 cycles). It was believed that the extra phase of Co3O4 may also participate in the electrochemical reactions due to its high electrochemically active nature. Benefiting from the appealing architectural features and striking synergistic effect, the integrated MnCo2O4/Co3O4 nanocomposite anode exhibits excellent electrochemical properties and high cycle stability for LIBs.

Stable Operation Induced by Plastic Crystal Electrolyte Used in Ni-Rich NMC811 Cathodes for Li-Ion Batteries.

The LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material has been of significant consideration owing to its high energy density for Li-ion batteries. However, the poor cycling stability in a carbonate electrolyte limits its further development. In this work, we report the excellent electrochemical performance of the NMC811 cathode using a rational electrolyte based on organic ionic plastic crystal N-ethyl-N-methyl pyrrolidinium bis(fluorosulfonyl)imide C2mpyr[FSI], with the addition of (1:1 mol) LiFSI salt. This plastic crystal electrolyte (PC) is a thick viscous liquid with an ionic conductivity of 2.3 × 10-3 S cm-1 and a high Li+ transference number of 0.4 at ambient temperature. The NMC811@PC cathode delivers a discharge capacity of 188 mA h g-1 at a rate of 0.2 C with a capacity retention of 94.5% after 200 cycles, much higher than that of using a carbonate electrolyte (54.3%). Moreover, the NMC811@PC cathode also exhibits a superior high-rate capability with a discharge capacity of 111.0 mA h g-1 at the 10 C rate. The significantly improved cycle performance of the NMC811@PC cathode can be attributed to the high Li+ conductivity of the PC electrolyte, the stable Li+ conductive CEI film, and the maintaining of particle integrity during long-term cycling. The admirable electrochemical performance of the NMC811|C2mpyr[FSI]:[LiFSI] system exhibits a promising application of the plastic crystal electrolyte for high voltage layered oxide cathode materials in advanced lithium-ion batteries.

Spatially Confined Fe7S8 Nanoparticles Anchored on a Porous Nitrogen-Doped Carbon Nanosheet Skeleton for High-Rate and Durable Sodium Storage.

Iron sulfides are widely explored as anodes of sodium-ion batteries (SIBs) owing to high theoretical capacities and low cost, but their practical application is still impeded by poor rate capability and fast capacity decay. Herein, for the first time, we construct highly dispersed Fe7S8 nanoparticles anchored on a porous N-doped carbon nanosheet (CN) skeleton (denoted as Fe7S8/NC) with high conductivity and numerous active sites via facile ion adsorption and thermal evaporation combined procedures coupled with a gas sulfurization treatment. Nanoscale design coupled with a conductive carbon skeleton can simultaneously mitigate the above obstacles to obtain enhanced structural stability and faster electrode reaction kinetics. With the aid of density functional theory (DFT) calculations, the synergistic interaction between CNs and Fe7S8 can not only ensure enhanced Na+ adsorption ability but also promote the charge transfer kinetics of the Fe7S8/NC electrode. Accordingly, the designed Fe7S8/NC electrode exhibits remarkable electrochemical performance with superior high-rate capability (451.4 mAh g-1 at 6 A g-1) and excellent long-term cycling stability (508.5 mAh g-1 over 1000 cycles at 4 A g-1) due to effectively alleviated volumetric variation, accelerated charge transfer kinetics, and strengthened structural integrity. Our work provides a feasible and effective design strategy toward the low-cost and scalable production of high-performance metal sulfide anode materials for SIBs.

Tailoring stress-relieved structure for ternary cobalt Phosphoselenide@N/P codoped carbon towards high-performance potassium-ion hybrid capacitors and potassium-ion batteries

The sluggish redox kinetics and severe volume changes of potassium-ion hosts are the challenging issues for potassium ion hybrid capacitors (PIHCs) and potassium-ion batteries (PIBs). Herein, a novel ternary cobalt phosphoselenide (CoPSe)@N/P co-doped carbon (NPC) composite with stress-relieved structure is introduced as anodes for PIHCs and PIBs. The ultrafine CoPSe nanocrystallites are embedded in the N and P codoped carbon matrix to form the spherical units. Then the resultant “nano-balls” are encapsulated in the tyre-like hollow framework to construct the “ball-in-tyre” (BIT) structure. Both dual carbon decorations and ultrafine crystals of BIT structure favor the fast electron/ion transports and significantly depress the internal stress. Meanwhile, the strong interfacial interaction between the ternary CoPSe crystal and N/P codopant carbon matrix favor the fast kinetics and high stability of the composite. For the first time, the [email protected] BIT composite is constructed via a facile bio-cooperated approach, where the local bio-combustion, in-situ phosphorization and selenization synchronize. Density function theory (DFT) result reveals the improved intrinsic conductivity, enhanced potassium adsorption and diffusion capabilities of the [email protected] heterostructure. Finite element simulations (FEA) suggest the depressed stress with uniform distributions internal the BIT structure during ion insertion/deinsertion processes. Electrochemical results demonstrate the superior high-rate capability and excellent cycling stability of [email protected] BIT composite in potassium-ion systems. Moreover, the PIHCs and PIBs full cell are fabricated based on the [email protected] BIT anodes. They exhibit the high energy density, high power density and high durability over long-term cycles. More impressively, both devices exhibit good abuse tolerance under diverse outside deformations or in a wide temperature range, which enable them promising power sources for diverse applications.

V3S4/PPy nanocomposites with superior high-rate capability as sodium-ion battery anodes

V3S4/PPy nanocomposites were synthesized and used as sodium-ion battery anodes, displaying high reversible capacity and superior high-rate capability.

Construction of hollow core–shell Sb2S3/S@S-doped C composite based on complexation reaction for high performance anode of sodium-ion batteries

Although the high-capacity Sb2S3-based anode materials for sodium-ion batteries can combine the advantages of multi-step conversion of Sb2S3 to Sb and alloying reaction between Sb and Na for improving the performance, the slow reaction kinetics, low electronic conductivity, and poor reversibility of the sodium storage process have limited their practical application. To effectively improve the electrochemical performance, a three-dimensional Sb2S3/S@S-doped carbon composite with a hollow core–shell structure based on the combination of template method and coupling reaction is successfully synthesized. By combining the finite element simulation, dynamic analysis, and density functional theory calculation, the respective roles of S-composite and hollow core–shell structure in boosting performance are revealed. The internal S and external S-doped carbon can interact with Sb2S3 to improve its reactivity with Na+, and effectively release the stress of Sb2S3 in the sodiation process. The S-doped carbon can accelerate Na+ diffusion and further stabilize the structure of Sb2S3. Benefited from the special structure, the as-prepared anode displays high reversible capacity, superior cycle performance and high rate capability. The assembled full battery also exhibits an excellent energy density under high power, and can still maintain a high reversible capacity of 310 mAh/g at 1 A/g over 500 cycles.

Preparation of carbon nanofiber supported Co nanoparticles for improving the electrochemical hydrogen storage properties of Co9S8 alloy

Co9S8 alloy was synthesized through mechanical ball milling, and cobalt/carbon nanofiber (Co/CNF) was prepared by the electrospinning process. The addition of Co and CNF increased the discharge capacity of Co9S8 to 563.4 mA/g. Furthermore, the composite electrode exhibited superior high-rate discharge capability, corrosion resistance, and other kinetic properties. CNF provides high conductivity and more reaction sites for Co nanoparticles. Co nanoparticles participate in redox reactions and show a catalytic effect. Moreover, the synergistic effect of CNF and Co also promotes the electrochemical hydrogen storage and kinetic performances of Co9S8 alloy.

Hierarchical hybrid architectures assembled from carbon coated Li3VO4 and in-situ generated N-doped graphene framework towards superior lithium storage

Owing to high specific capacity (394 mA h g −1 based on a two-electron reaction), good ionic conductivity and suitable working potential (~ 0.8 V), Li 3 VO 4 (LVO) has been recently considered as a promising intercalation anode material for lithium-ion batteries (LIBs). Such material, however, suffers from poor electronic conductivity, thus limiting its practical applications. Herein, we develop a facile self-template strategy for constructing 3D hierarchical LVO/C hybrids assembled from carbon-coated LVO and in-situ generated N-doped graphene framework. Such hybrids not only offer an interconnected 3D conductive network, but also afford intimate contact between active components and conductive scaffolds, thus realizing a high-efficiency electron/ion transport system. When employed as anode for LIBs, the resulting product exhibits reversible capacities of 347.6 mA h g −1 at 0.5 A g −1 and 206.8 mA h g −1 at 4 A g −1 , and a capacity retention of 75.3 % after 1000 cycles at 1 A g −1 . This work provides a facile and green strategy for building 3D multiscale hierarchical hybrids, which could be extended to prepare other nanocomposites for energy-related applications. • Develop N-doped graphene framework encapsulated Li 3 VO 4 by a self-template strategy. • Such hybrids provide a 3D electron/ion conductive network. • Such hybrid can well accommodate the structural strain during cycles. • Realize superior high-rate capability and long-term cyclability.

Superior sodium storage in anatase/bronze TiO2 nanofibers through surface phosphorylation

TiO2-based nanostructure has been reported as one of the most developable anode materials for sodium-ion batteries, but its low capacity and poor rate capability bring an unavoidable challenge and impedethepractical application. In this study, surface phosphorylated TiO2 nanofibers with anatase/bronze binary-phase are fabricated using ion exchange-annealing treatment and subsequent phosphorylation. The resulting nanofiberscan serve as an efficient electrode material for sodium storage, affording a reversible capacity of 224.7 mAh g−1at 200 mA g−1 and a superior high-rate cycling capability of 108.9 mAh g−1 at 2000 mA g−1 after 1000 cycles.XPS and HRTEM reveal that the synthesized SP-TiO2-A/B nanofibers present heterojunction-boundary between anatase/bronze binary-phase and well-crystallized internal-structure with disordered/amorphous surface, and a high ratio of active surface was motivated through phosphorylation and Na+ion storage behavior was efficiently modulated. The surface phosphorylation engineering provides a promising strategy to develop Na-storage electrodes with superior electrochemical performance.

Effect of heat treatment on the electrochemical performance of V2O5·nH2O as a cathode material for aqueous rechargeable zinc ion batteries

The influence of heat treatment (100 °C, 150 °C, 200 °C, 300 °C, and 400 °C) on the structure and the zinc ion storage performance of V2O5·nH2O is explored. The results show that the interlayer water content, interlayer distance, and V4+ content in V2O5·nH2O can be regulated by heat treatment. Electrochemical characterization demonstrates that the as-prepared vanadium pentoxide without heat treatment shows rather poor cycling stability (only 56 m Ah g−1 after 600 cycles at 0.5 A/g). After being heat treated in the temperature range of 100 to 200 °C, the zinc ion storage performance of vanadium pentoxide can be enhanced dramatically. Particularly, the vanadium pentoxide after being heat-treated at 150 °C exhibits the best cycling stability (179 mA h g−1 after 600 cycles at 0.5 A/g), superior high-rate capability (117 mA h g−1 at 3.0 A/g), and faster electrochemical reaction kinetics. The results reported in this work could provide clues for regulating and optimizing the electrochemical performance of vanadium pentoxide as a cathode material for ZIBs.

GaSb nanocomposite: New high-performance anode material for Na- and K-ion batteries

As representative next-generation secondary battery systems, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are key candidates to achieve zero-carbon emission. Herein, we introduce a versatile GaSb nanocomposite anode for SIBs and PIBs. The performance and phase transition mechanism for GaSb, pure Ga, and Sb with Na and K ions are evaluated. Furthermore, three-step nanoconfinement and stabilization of GaSb crystallites are achieved in the GaSb nanocomposite. The nanostructure of the GaSb nanocomposite, consisting of approximately 2–4 nm GaSb crystallites uniformly distributed in an amorphous carbon matrix, promotes the electrochemical reaction kinetics with Na and K ions, and the chemical and mechanical stabilities of the GaSb nanocomposite electrodes. The GaSb nanocomposite anode possesses highly reversible initial volumetric and gravimetric capacities and superior high-rate capabilities. In this study, we offer new insights into the phase transition mechanisms of GaSb with Na and K ions and promising performance GaSb nanocomposite anodes for SIBs and PIBs.

Construction of simultaneous modified Na3V2(PO4)3/C cathode with K/Zr substitution and carbon nanotubes enwrapping for high performance sodium ion battery

Na 3 V 2 (PO 4 ) 3 (NVP) has been deemed to be a prospective cathode material due to the unique NASICON-type framework for sodium ion battery (SIB). Nevertheless, the inferior intrinsic conductive property seriously impedes the development of NVP. Herein, the K/Zr co-substituted and carbon nanotubes (CNTs) enwrapped NVP/C composite is successfully synthesized through a facile sol-gel route. Notably, the introduced K + in Na1 site possesses a pillar effect on the crystal structure to efficiently stabilize the framework. Meanwhile, Zr 4+ with larger ionic radius successfully replaces of V 3+ , which is beneficial to expanding the interplanar spacing to facilitate the migration of Na + . Moreover, the enwrapped tubular CNTs can restrict the agglomerations of active grains to diminish the pathways for ionic and electronic transportation. Synthetically, the CNTs and amorphous coated carbon layers jointly construct a cross-linked 3D network to provide accelerated channels for electronic transportation. Consequently, the modified Na 2.96 K 0.04 V 1.93 Zr 0.0525 (PO 4 ) 3 /C@CNTs composite exhibits superior electrochemical performance with excellent kinetic properties. Accordingly, it delivers a great capacity value of 110.8 mAh g −1 at 0.1 C. Besides, it exhibits a reversible capacity of 102 mAh g −1 at 2 C and maintains 89.7% after 300 cycles. As for a higher rate of 5 C, it releases an initial capacity of 99 mAh g −1 and a high retention of 90.9% can be obtained after 1300 cycles. Significantly, the optimized sample delivers a high capacity of 91.2 mAh g −1 at an ultra-high rate of 60 C and sustains 78.3% after 3000 cycles. Furthermore, the symmetric full cell is successfully fabricated and reveals superior high-rate capability with excellent stability. Therefore, this modified Na 2.96 K 0.04 V 1.93 Zr 0.0525 (PO 4 ) 3 /C@CNTs composite would be a promising cathode material for practical applications in SIB.

Design and synthesis of high-energy-density heterostructure Na0.7MnO2–Li4Mn5O12 cathode material for advanced lithium batteries

The construction of the heterostructure, 0.6Na0.7MnO2–0.4Li4Mn5O12, can form a synergistic effect, which exhibits superior high-rate capability and excellent cycle performance.

Design of Ti4+-doped Li3V2(PO4)3/C fibers for lithium energy storage

In this work, we propose a facile approach to fabricate Ti4+-doped Li3V2(PO4)3/C (abbreviated as C-LVTP) nanofibers using an electrospinning route followed by a high temperature treatment. In this designed nanocomposite, the ultrafine LVTP dots are homogeneously dispersed into one-dimensional carbon nanofibers and the Ti4+ doping does not destroy the crystal structure of monoclinic Li3V2(PO4)3. Compared to the undoped Li3V2(PO4)3/C (abbreviated as C-LVP), the as-fabricated C-LVTP fibers present higher reversible capacity, superior high-rate capability as well as better cyclic property. Especially, the C-LVT7%P cathode delivers not only high capacities of 187.2 and 160.3 mAh g−1 at 0.5 and 10 C respectively, but also stable cyclic property with the reversible capacity of 135.8 mAh g−1 at 20 C following 500-cycle spans. The good battery characteristics of C-LVT7%P can be mainly ascribed to Ti4+ doping, which can increase the electrical conductivity and Li+ diffusion coefficient.

A Fast and Scalable Pre-Lithiation Approach for Practical Large-Capacity Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) bridge the gap between lithium-ion batteries (LIBs) and electrical double-layer capacitors (EDLCs) owing to their unique energy storage mechanisms. From the viewpoints of electrode materials and cell design, the pre-lithiation process is indispensable for improving the working voltage and energy density of LICs. However, the conventional physical short-circuit (PSC) method is time-consuming, which limits the mass-production of practical large-capacity LIC cells. Three alternative pre-lithiation protocols have been proposed, combining the PSC protocol and electrochemical approaches to shorten the pre-lithiation time. The prototype LIC pre-lithiated by using the open-circuit potential cycling (OPC) protocol has the lowest internal resistance and superior high-rate capability (even at 200C-rate). The 900-F large-capacity laminated LIC cells have been assembled and pre-lithiated to validate the feasibility of this method. The pre-lithiation time has been reduced from 470 h (PSC protocol) to 19 h (OPC protocol). This combined protocol is presumed to counteract the voltage loss and enhance the Li+ ion diffusion between multiple anode electrodes during the pre-lithiation process.

Enhanced lithium ions storage performance of Fe2(SO4)3 anode material synthesized by solution calcination route with the assistance of melamine

Exploring novel electrode materials with high capacity, good cyclability, and low cost is very crucial for the development of lithium-ion batteries (LIBs). Herein, Fe2(SO4)3 anode material is synthesized by a facile solution calcination route with the assistance of melamine. The Fe2(SO4)3 sample synthesized with the assistance of melamine exhibits much superior high-rate capability (with a reversible capacity of 621 mA h g−1 at 5.0 A g−1) and long-term cyclability (maintaining a reversible capacity of 755 mA h g−1 after 600 cycles at 1.0 A g−1). Moreover, the Fe2(SO4)3 sample displays significant pseudocapacitive behavior during the discharge/charge processes; the lithium ions diffusion coefficient is evaluated to be in the range of 10−11 ∼ 10−13 cm2 s−1.

Gd3+-doped NaTi2(PO4)3@C negative material with superior Na-storage property for sodium-ion batteries

The pristine NaTi2(PO4)3 negative electrode material has a poor electrical conductivity, which significantly inhibits its application in sodium-ion batteries. Herein, carbon coating and Gd3+ doping are simultaneously applied to promote the electrical conductivity of NaTi2(PO4)3 through a simple sol-gel approach. The conductive carbon coating promotes apparent conductivity, while Gd3+-doping effectively improves intrinsic conductivity. Therefore, the resulting Gd3+-doped NaTi2−xGdx(PO4)3@C (x=1%, 3%, 5%, 7%) composites display superior high-rate capabilities for sodium energy storage. A typical obtained NaTi1.95Gd0.05(PO4)3@C anode presents high capacities of 105.9 and 93.1 mAh g−1 at 5 and 10 C, respectively. Furthermore, this anode shows a high capacity retention ratio of 95.2% at 20 C over 500 cycles. These results suggest that this carbon coating and doping strategy is highly effective and can be adopted to enhance the battery properties of other electrode materials.

Effects of Ti substitution for Zr on the electrochemical characteristics and structure of AB2-type Laves-phase alloys as metal hydride anodes

The structural composition and electrochemical capacity of four AB2 Laves-type intermetallic alloys with various Ti/Zr ratios (TixZr1−xLa0.03Ni1.2Mn0.7V0.12Fe0.12, x = 0.12, 0.15, 0.18, and 0.22) were investigated in this study. The alloys were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. These data revealed the coexistence of the main phase of the C15-type FCC Laves-type AB2 compounds with a secondary La–Ni intermetallic that was present in minor amounts. Increasing the Ti substitution for Zr caused the gradual shrinkage of the unit cells of the C15 phase. The neutron powder diffraction studies demonstrated that in the trihydride (Ti, Zr, V)(Ni, Mn, Fe, V)2D3.2, D atoms filled A2B2 tetrahedra, whereas V atoms occupied not only conventional 16d sites but also partially replaced Zr/Ti at 8a sites. All studied alloys showed similar activation behaviors, wherein four cycles were required to realize the highest electrochemical capacity of the anodes. The Ti12/Zr88 alloy demonstrated excellent full discharge capacity that reached 466 mAh/g. The Ti22/Zr78 alloy electrode exhibited good cycling stability (retention rate of ~71%) after 500 cycles and a superior high-rate discharge capability (retention rate of ~71%) at a discharge current density of 400 mA/g. The cycling of the Ti22/Zr78 alloy electrode was studied by electrochemical impedance spectroscopy (EIS) to understand the reasons for the deterioration of cycling capacity, which was related with the pulverization of the alloys and increase in irreversible capacity.

Electrochemical performance of Fe2(SO4)3 as a novel anode material for lithium-ion batteries

Exploring new electrode materials with high capacity, good cyclability, and low cost is of great importance for the development of lithium-ion batteries (LIBs). Herein, the lithium storage performance of Fe2(SO4)3 as an anode material for LIBs is investigated for the first time. The microstructure of the Fe2(SO4)3 sample is analyzed by XRD, SEM, TEM, and XPS measurements. The lithium storage performance of the Fe2(SO4)3 sample is characterized by discharge/charge, CV, EIS, and GITT tests. It demonstrates that the Fe2(SO4)3 has a high lithium storage capacity (delivering a stable reversible capacity of 610 mA h g−1 at 500 mA g−1), outstanding rate capability (maintaining a capacity of 400 mA h g−1 at 7000 mA g−1) and excellent cyclability (with a reversible capacity of ~540 mA h g−1 after 1000 cycles at 1000 mA g−1). The Fe2(SO4)3 electrode exhibits significant pseudocapacitive behavior during discharge/charge processes, which partially accounts for the superior high rate capability and cyclability. The lithium ions diffusion coefficient evaluated by galvanostatic intermittent titration technique (GITT) ranges from 10−11 to 10−13 cm2 s−1. The results reported in this work could provide clues for exploring novel high-performance anode materials from transition metal sulfates.