Average Capacity Loss Research Articles

Joint Time-Frequency Signal Analysis of Li-Ion Batteries

Measurements acquired from batteries, such as voltage-time and capacity-time signals, offer valuable insights into their cyclability performance. While analyzing these signals in the time domain provides an understanding of global characteristics, scrutinizing local behavior is crucial for detecting issues like battery fading. In this context, we delve into the application of short-time Fourier transform for time-frequency deconstruction of galvanostatic charge/discharge signals, using lithium-sulfur batteries as an illustrative example. Spectrograms resulting from this analysis unveil the evolving frequency content of signals throughout the battery's lifespan, facilitating the identification of critical changes in the response and early detection of issues leading to fading and potential default. Simultaneously, the stability analysis of the dynamic response of red phosphorus and sulfide polyacrylonitrile (RP-SPAN) composite, a promising anode material for lithium batteries, can also be studied using Fourier transform analysis. Our study employs transfer function stability analysis, Kramers-Kronig integral relations, and differential capacity analysis to assess the cell's behavior in both frequency and time domains. Parameters such as stationarity, stability, linearity, dissipation, and degradation are scrutinized over extended charge/discharge cycles. Results reveal a highly nonlinear and time-variant system at low frequencies, aligning with the observed 0.21% average capacity loss per cycle. Our results indicate that short-time Fourier transform could provide insightful information for analyzing battery health.

Promoting Polysulfide Redox Reactions through Electronic Spin Manipulation.

Catalytic additives able to accelerate the lithium-sulfur redox reaction are a key component of sulfur cathodes in lithium-sulfur batteries (LSBs). Their design focuses on optimizing the charge distribution within the energy spectra, which involves refinement of the distribution and occupancy of the electronic density of states. Herein, beyond charge distribution, we explore the role of the electronic spin configuration on the polysulfide adsorption properties and catalytic activity of the additive. We showcase the importance of this electronic parameter by generating spin polarization through a defect engineering approach based on the introduction of Co vacancies on the surface of CoSe nanosheets. We show vacancies change the electron spin state distribution, increasing the number of unpaired electrons with aligned spins. This local electronic rearrangement enhances the polysulfide adsorption, reducing the activation energy of the Li-S redox reactions. As a result, more uniform nucleation and growth of Li2S and an accelerated liquid-solid conversion in LSB cathodes are obtained. These translate into LSB cathodes exhibiting capacities up to 1089 mA h g-1 at 1 C with 0.017% average capacity loss after 1500 cycles, and up to 5.2 mA h cm-2, with 0.16% decay per cycle after 200 cycles in high sulfur loading cells.

Bismuth-constructed high-speed channeled for Bi/Sb2SnO5@PCFs composite as high-rate and long-life anode for sodium-ion batteries

To cope with the charging-time and driving-range issues of the power batteries, a composite and phase modification tactics is manifested to increase the cycling stability and rate capability of the Sb2SnO5 (SSO) anode for sodium-ion batteries (SIBs). The as-fabricated Bi/SSO@PCFs composite with Bi nanocrystals homogeneously dispersed on and around the SSO surface is prepared by an electrospinning method. The excellently dispersed Bi nanocrystals realize an effective contact with SSO, which effectively lowers the electron conduction barriers and promotes the sodium ion release as well as the transport upon the desodiation/sodiation process, increasing the rate capacity and cycle stability of the SSO anode. Importantly, a high-speed ion channel is constructed through the special layered Bi, and SbBi phase. The prepared Bi/SSO@PCFs anodes deliver a high rate capacity up to 25 A g−1 and long cycle life of 5000 cycles with 83 % capacity retention rate, sustaining an average capacity loss of 0.0034 % for each cycle. Particularly, the intercalation of Na+ between layer-structure Bi and SbBi galleries provides a good basis for excellent cycle performance due to small volume change and unobstructed ion channels. This finding provides an effective strategy to establish ion transport highways, which essentially increase the rate-capacity and cycle-life of the SSO-based anodes for SIBs.

Phosphorus-doped TiO2 mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2 as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2 mesoporous nanocrystals (P-TMC) with ultrafine size of 2–8 nm and high specific surface area (234.164 m2 g–1) has been synthesized. It is formed through a hydrothermal process and NaBH4 assisted heat treatment for anatase defective TiO2 (TiO2–x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material’s electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g–1 at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g–1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g−1 can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

Synthesis, characterization and uptake studies of diglycolamic acid and diglycolamide analogs adsorbents for extraction of rare earth elements

Tetraalkyldiglycolamides are known for their high extracting efficiency of rare earth elements (REEs) from nitric acid solutions (1–6 mol/L). Nevertheless, solid-phase extractants based on diglycolamides (DGA) are poorly studied for REEs extraction. This paper explores the design and synthesis of novel REEs adsorbents by grafting silica with diglycolic acid-based ligands. The newly developed solid-phase materials were investigated for their potential to effectively separate REEs from various media. The functionalization of the silica with different ligands was quantified, and the adsorbents' extraction capacities and selectivity for REEs over Calcium (Ca2+), Aluminium (Al3+) and Iron (Fe3+) were evaluated. Si-NH-DGA emerged as the most efficient adsorbent for Gd3+ extraction, exhibiting a remarkable capacity of 44 mg/g at pH 4–6. However, modifications involving ether oxygen substitution with a methylamino group or sulfur led to reduced extraction efficiencies. Si-NH-DGA-NMe2 demonstrated strong binding of REEs in nitric acid solutions (1–3 mol/L HNO3) with corresponding adsorption capacities for Y3+, La3+, Gd3+ and Yb3+ being 16.3, 14.2, 22.8, and 30.2 mg/g, respectively. Furthermore, it displayed remarkable selectivity for REEs over Ca2+. The equilibrium extraction for Gd occurred within 60 min for Si-NH-DGA and Si-NH-DGA-NMe2 under their respective optimal conditions. Disodium EDTA solution demonstrated a high stripping efficiency for Gd3+ in the Si-NH-DGA-NMe2 column extraction, yielding a significant concentration factor (CF = 85). In the same column, following five cycles of loading/stripping of Gd3+, there was an average capacity loss of 6%. Si-NH-DGA-NMe2 emerged as a promising material for solid-phase extraction from concentrated nitric acid solutions, characterized by high capacity and good selectivity towards middle and heavy REEs. This structure has the potential to be further optimized for the development of a solid-phase extraction column for REEs separation and purification. The findings also highlight the potential of Si-NH-DGA-NMe2 as a candidate for REEs adsorption for potential industrial applications and the purification of acidic waste solutions.

Ageing and energy performance analysis of a utility-scale lithium-ion battery for power grid applications through a data-driven empirical modelling approach

Energy storage systems are becoming one of the most relevant technologies to effectively support renewable energy source (RES) deployment at large. The present work proposes a detailed ageing and energy analysis based on a data-driven empirical approach of a real utility-scale grid-connected lithium-ion battery energy storage system (LIBESS) for providing power grid services. The system under investigation is an operative utility-scale LIBESS integrated with a multi-MW PV plant and connected to the medium voltage network, located in Southern-Italy. The ageing and energy analysis has been performed using data measured by the supervisory control and data acquisition (SCADA) system directly connected with the LIBESS. This large amount of data is collected in a cloud database and then elaborated using proper software tools. This experimental campaign applied on a commercial LIBESS covers the impact of degradation mechanisms, such as cycle and calendar ageing, the battery and global system efficiency as well as the role of auxiliaries' power consumption under normal and power grid services operations. Thanks to the low complexity of the proposed data-driven model, it could be easily replicated in any other LIBESS facility, both operative in real-world framework and in laboratory context. The state-of-health (SOH) estimated by the degradation model implemented in this work after 3 years of operations and after 356 full-cycles equivalents is equal to 95.88 %, with an average capacity loss compared to the nominal capacity of about 1.37 % per year. Energy analysis revealed an average system global efficiency of 85 % for operations close to the nominal power that decreases to 65 % for operations at low power rates. While considering the grid network services operations, the power grid applications investigated are primary frequency regulation, secondary voltage regulation and PV unbalances reduction. Our results show that primary frequency regulation is the most efficient service in terms of ageing and energy performances. It has been evaluated a capacity loss of 0.03 kWh per each full-cycle equivalent performed during primary frequency regulation. Differently, secondary voltage regulation and PV unbalances reduction present a capacity loss of 0.1 kWh and of 0.05 kWh per each full-cycle equivalent, respectively. At the same time, the global efficiency of primary regulation (around 83 %) is remarkably higher compared to secondary voltage regulation (about 47 %) and to PV unbalances reduction (about 55 %). Results support the relevance to identify the most impacting key performance indicators for effective exploitation of LIBESS in power system and network services applications.

CoSe2 nanoparticles anchored on porous carbon network structure for efficient Na-ion storage

Cobalt selenide, as a star material in battery industry, has attracted much attention. However, when it is applied solely in sodium ion batteries, it will cause large volume expansion and material agglomeration, which will seriously affect the overall performance of batteries. In this work, we use ice bath impregnation to combine CoSe2 nanoparticles with porous nitrogen-doped carbon networks (NC) as advanced anodes for ultra-long cycle life sodium ion batteries (SIBs). CoSe2 nanoparticles are evenly attached to NC with strong interfacial contacts in CoSe2@NC. The strong contact of CoSe2 on the porous carbon network, along with the carbon network's unique network cross-linking structure, results in rapid electron transfer and Na ion diffusion kinetics of CoSe2@NC, resulting in superior electrochemical performance. Besides, we have synthesized CoSe2@NC with different loading by changing Co2+ concentration. The results show that CoSe2@NC anode thus provides a high reversible capacity of 406 mAh/g. In addition, at high current 5 A/g, it can keep a reversible capacity of 300 mAh/g after 4500 cycles with an average capacity loss of less than 0.01 % per cycle. The excellent anchoring structure enables it to form stable solid electrolyte film (SEI) and reduce the amount of dead sodium in the first charge–discharge process, showing high Initial Coulombic Efficiency (ICE) (89.2 %). Finally, CoSe2@NC and Na3V2(PO4)3 (NVP) are assembled into a full cell and the results shows an ultra-long cycle stability at 0.1 A/g. This strategy will facilitate the application of transition metal selenides in next-generation energy storage systems.

Mitigating Polysulfide Shuttles with Upcycled Alkali Metal Terephthalate Decorated Separators

High energy density lithium–sulfur batteries (LSBs) are a potential replacement for lithium-ion batteries (LIBs). However, practical lifetimes are inhibited by lithium polysulfide (LiPS) shuttling. Concurrently, plastic waste accumulation worldwide threatens our ecosystems. Herein, a fast and facile strategy to upcycle polyethylene terephthalate (PET) waste into useful materials is investigated. Dilithium terephthalate (Li2TP) and dipotassium terephthalate (K2TP) salts were synthesized from waste soda bottles via microwave depolymerization and solution coated onto glass fiber paper (GFP) separators. Salt-functionalized separators with Li2TP@GFP and K2TP@GFP mitigated LiPS shuttling and improved electrochemical performance in cells. Pore analysis and density functional theory (DFT) calculations indicate the action mechanism is synergistic physical blocking of bulky LiPS anions in nanopores and diffusion inhibition via electrostatic interactions with abundant carboxylate groups. LSBs with K2TP@GFP separator showing highest LiPS affinity and smallest pore size demonstrated enhanced initial capacity as compared to non-modified GFP by 5.4% to 648 mAh g−1, and increased cycle 100 capacity by 23% to 551 mAh g−1. Overall, K2TP@GFP retained 85% of initial capacity after 100 cycles with an average capacity fading of 0.15% per cycle. By comparison, GFP retained only 73% of initial capacity after 100 cycles with 0.27% average capacity loss, demonstrating effective LiPS retention.

Polyoxometalates-rich separator for fast polysulfide conversion kinetics and dense lithium deposition toward stable Li–S batteries

Lithium−sulfur batteries have great potential in the field of next-generation energy-storage devices owing to their high theoretical energy density. However, the polysulfide intermediates shuttling seriously result in fast capacity degradation and poor cycling stability, thus hindering their commercial applications. In this paper, we choose polyvinylidene fluoride containing polar functional groups in its polymeric chain as polymer carrier to construct the H 3 PW 12 O 40 firmly and uniformly decorated nanofibers membrane by electrospinning technique. Benefiting from the feature of “electron sponges”, H 3 PW 12 O 40 can act as polysulfide mediator to significantly facilitate the liquid-liquid reaction kinetics of polysulfides in the electrode/separator interface. Besides, fewer cracks, pulverization and adhesion of dead lithium particles occurred in the lithium metal anode, demostrating a more homogeneous Li-ion flux distribution after using this membrane with three-dimensional network structure and abundant redox active sites. The cell with such bifunctional separator delivers a specific capacity of 966 mAh g -1 at 1.0 C, and retained a capacity of 682 mAh g -1 after 300 cycles, corresponding to an average capacity loss of 0.09% per cycle. The Keggin-type H 3 PW 12 O 40 /PVDF nanofiber membrane in Li-S batteries can not only possess enhanced sulfur redox kinetics and lithium-ion transport kinetics but also can protect the lithium metal anode. • The PW 12 -PVDF/PP separator could regulate the Li + flux to induce Li nucleation. • The PW 12 -PVDF/PP separator improves the catalytic effect of the polysulfides. • The Li–S cell with PW 12 -PVDF/PP separator shows good electrochemical performances.

Constructing hollow nanotube-like amorphous vanadium oxide and carbon hybrid via in-situ electrochemical induction for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries receive more and more attentions on account of their low cost, high theoretical density and inherent safety. Nevertheless, the lack of suitable cathode materials with excellent performance still severely impedes the development of aqueous zinc-ion batteries. Herein, an in-situ electrochemical induction strategy is developed to prepare hollow nanotube-like amorphous vanadium oxide and carbon (a-V2O5@C) hybrid and its electrochemical performance is investigated comprehensively as cathode materials for aqueous zinc-ion batteries. Benefitting from the unique amorphous structure of V2O5 and intimate contact between amorphous V2O5 and carbon, the a-V2O5@C hybrid possess the abundant ion storage sites, isotropic ion diffusion routes and excellent conductivity. As a result, the a-V2O5@C hybrid cathode shows outstanding specific capacity of 448 mAh g−1 at 0.15 A g−1. Impressively, the a-V2O5@C hybrid cathode exhibits superior cycling stability, even when cycling at high current density of 10 A g−1, that the 96.5% specific capacity retention can be gained over 1500 cycles, corresponding to an average specific capacity loss of only 0.0023% per cycle. Furthermore, the mechanism involved is illustrated by systematical characterizations. Therefore, this work affords a new way for developing high-performance cathode materials for aqueous zinc-ion batteries.

Carbon Nanotube-Modified Nickel Hydroxide as Cathode Materials for High-Performance Li-S Batteries.

The advantages of high energy density and low cost make lithium–sulfur batteries one of the most promising candidates for next-generation energy storage systems. However, the electrical insulativity of sulfur and the serious shuttle effect of lithium polysulfides (LiPSs) still impedes its further development. In this regard, a uniform hollow mesoporous Ni(OH)2@CNT microsphere was developed to address these issues. The SEM images show the Ni(OH)2 delivers an average size of about 5 μm, which is composed of nanosheets. The designed Ni(OH)2@CNT contains transition metal cations and interlayer anions, featuring the unique 3D spheroidal flower structure, decent porosity, and large surface area, which is highly conducive to conversion systems and electrochemical energy storage. As a result, the as-fabricated Li-S battery delivers the reversible capacity of 652 mAh g−1 after 400 cycles, demonstrating excellent capacity retention with a low average capacity loss of only 0.081% per cycle at 1 C. This work has shown that the Ni(OH)2@CNT sulfur host prepared by hydrothermal embraces delivers strong physical absorption as well as chemical affinity.

Behaviour of retrofited precast UHPC and Ni-Ti SMA column-to-foundation connection with CFRP wrapping layers

Four precast column-to-foundation connection specimens, previously tested under lateral reversed cyclic loading and constant axial load (first-stage tests), were repaired with Carbon Fibre Reinforced Polymer (CFRP) layers in the areas where plastic hinges had formed and were retested under the same loads (second-stage tests). The columns were originally manufactured with ultrahigh-performance concrete (UHPC) with high stee-fibre content (volumetric steel/fibre ratio 1.9%). The steel bars in the connection were replaced with superelastic Ni-Ti SMA bars that crossed the column/foundation interface. Two types of connection between the precast column and the foundation were analysed: protruding bars and smooth pocket bars (SP). The specimens were subjected to the same constant level of relative axial load in both the first and second-stage tests. The objective was to determine whether the initial performance of precast UHPC and SMA reinforced column-to-foundation connections against lateral cyclic loads can be restored after a seismic event by means of simple and economic retrofitting. The effectiveness of the number of strengthening CFRP layers was also studied (two or three CFRP wrapping layers) for each column-to-foundation connection type. The main results for PB and SP connection specimens with respect to the original specimens were respectively: an average strength capacity loss of 8% and 19%, displacement ductility increase of 8% and 42%, dissipated energy 48% and 53% higher and initial stiffness 9.5% and 21% lower. No significant differences were observed in the repairs done with two or three CFRP wrapping layers.

Controllable preparation of dual-phase VC-C through in-situ electroconversion for lithium storage

Transition metal carbides as promising electrode materials for lithium ions batteries (LIBs) have attracted wide attentions due to high conductivity and capacity. In this paper, dual-phase VC-C as anode materials of LIBs is designed and synthesized through green and controllable in-situ electroconversion from CO 2 and NaVO 3 in molten salt. Three products including dual-phase VC-C (VC–C), vanadium carbide doped by carbon (VC-DC) and carbon doped by vanadium carbide (C-DVC), are prepared by the effective regulation during molten salt electrolysis. It is confirmed that dual-phase VC-C as anode materials of LIBs exhibits the best charge/discharge performance and cycling stability. At current density of 0.1 A g −1 , the stable reversible capacity can reach to 652.3 mAh g −1 . Even at a high current density of 1.0 A g −1 , the reversible capacity maintains about 300 mAh g −1 after 600 cycles. The capacity retention is as high as 98.4%. The average capacity loss of per cycle is only 0.0027%. The dual-phase VC-C through sustainable electroconversion from CO 2 and NaVO 3 in molten salt is of good promising anode materials for LIBs.

A surface-nitridized 3D nickel host for lithium metal anodes with long cycling life at a high rate.

Three dimensional (3D) metal structures such as nickel (Ni) and copper (Cu) frames have long been regarded as a good host for lithium (Li) metal. However, Li deposition on different metals often causes obvious over-potential, affecting the electrode performance in lithium metal batteries. Here, a Ni-N-O interface was created by surface nitridation to the Ni micro-particles, which were made into 3D current collectors. The directly grown Ni3N created a thin and lithiophilic layer containing dense Li nucleation sites. The homogeneous distribution of amorphous Ni3N and NiO at the interface allowed for a fast transfer of both electrons and ions, and thus facilitated smooth and even plating/stripping of lithium. High cycling stability and rate capability were simultaneously achieved. The 3D Li@N-Ni anode exhibited an extremely low voltage hysteresis of ∼10 mV over 850 h in a symmetric cell. The full battery paired with LiFePO4 achieved steady cycling at 5C for 1500 cycles, with coulombic efficiency constantly higher than 99.2% and an average capacity loss of 0.027 mA h g-1 per cycle, demonstrating a rational strategy for the design and fabrication of efficient lithium anodes for practical applications.

Li1+xMn2O4 synthesized by in-situ lithiation for improving sulfur redox kinetics of Li-S batteries

Lithium-sulfur (Li-S) battery is one of the most promising candidates for the next generation energy storage systems. However, the inherent slow redox kinetics of sulfur leads to limited rate performance, low discharge capacity and rapid capacity fading. Herein, the Li1+xMn2O4 material produced by in-situ lithium intercalation of LiMn2O4 before 2.5 V is selected to improve the performances of Li-S batteries. First-principles calculations show that Li1+xMn2O4 can improve electronic conductivity and chemical adsorption. Electrochemical characterizations further confirm that lithiated material provides a fast conversion kinetics for LiPSs and a low barrier of lithium-ion diffusion. As a result, the Li-S battery incorporating Li1+xMn2O4 presents excellent rate performance with a discharge capacity as high as 915 mAh g − 1 at 2 C rate. At the same time, the battery maintains a high reversible capacity of 531 mAh g − 1 after 1000 cycles at 1 C rate, and the average capacity loss per cycle is only 0.047%. This work can improve the redox kinetics of sulfur cathodes and provide a new path for the advancement of high-performance Li-S batteries.

Electrochemical stability analysis of red phosphorus-based anode for lithium-ion batteries

Red phosphorus and sulfurized polyacrylonitrile (RP-SPAN) composite has recently shown promising results as an anode material in lithium-ion battery applications. However, the stability analysis of its dynamic response has not been investigated yet. In this study we use the transfer function stability analysis, the Kramers-Kronig (KK) integral relations, and the differential capacity analysis to evaluate the cell’s behavior in both frequency and time domains in terms of stationarity, stability, linearity, as well as dissipation and degradation with extended charge/discharge cycling. The results show that the system is highly nonlinear and time-variant at the low-frequencies spectrum which is in line with the 0.21% average capacity loss per cycle computed from consecutive charge/discharge measurements. We propose using a modified constant phase element in which magnitude and phase, and thus real and imaginary parts of the spectral response are decoupled to fit the low-frequency, non-KK-compliant data.

Ultrafine Sodium Sulfide Clusters Confined in Carbon Nano-polyhedrons as High-Efficiency Presodiation Reagents for Sodium-Ion Batteries.

Sodium loss at the anode in the initial sodiation process significantly reduces the energy density of sodium-ion batteries (SIBs). Here, a high-capacity Na2S/C nanocomposite featuring ultrafine Na2S nanoclusters (<2 nm) confined in ZIF-8-derived microporous N-doped carbon is fabricated and employed as a cathode presodiation reagent to compensate for this sodium loss and increase the energy density of SIBs. The ultrafine size of Na2S enables fast reaction kinetics for sodium extraction and the carbon matrix provides good electronic conductivity. Also, the overall particle size of the Na2S/C nanocomposite (∼40 nm) is close to that of conductive additive. The above features enable it to replace a partial amount of conductive additive and compensate for the sodium loss at the anode concurrently. As a demonstration, the Na3V2(PO4)3 electrode with 5 wt % Na2S/C and 5 wt % carbon black was fabricated, and it displayed a 19 mAh g-1 higher initial charge specific capacity than that of the counterpart with 10% carbon black without the addition of Na2S/C, realizing an increased energy density from 178 to 263 Wh kg-1 in the full cell configuration pairing with a hard carbon anode. Moreover, a stable cycling performance up to 200 cycles with an average capacity loss of 0.024 mAh g-1 per cycle was achieved for the presodiated Na3V2(PO4)3 electrode.

Low crystalline 1T-MoS2@S-doped carbon hollow spheres as an anode material for Lithium-ion battery

A low crystalline 1T-MoS2@S-doped carbon (MoS2@SC) composite was successfully synthesized via a facile hydrothermal process. The composite is comprised by few-layer 1T-MoS2 nanosheets covered by an amorphous carbon layer with an expanded interlayer d-spacing of 1.01 nm. This structure is conducive to the fast transport of lithium-ions and volume accommodation during the charge–discharge process when the composite is applied as an anode material for LIBs. Additionally, the high conductivity and layered structure of 1T-MoS2 also facilitate fast of ion/electron transport, contributing to the improvement of the electrochemical properties. Therefore, this material demonstrated a high rate performance and excellent cycling stability, with the capacities of 847 and 622 mA h g−1 achieved at the current densities of 0.2 A g−1 and 2 A g−1, respectively. Even at a larger current density of 2 A g−1, MoS2@SC delivered a high reversible capacity of 659 mA h g−1 with an average capacity loss of 0.006% per cycle after 500 cycles.

TiO2 quantum dots confined in 3D carbon framework for outstanding surface lithium storage with improved kinetics

Pseudocapacitive lithium storage is an effective way to promote the improvement of electrochemical performance for lithium ion batteries. However, the intrinsically sluggish lithium ionic diffusion and the low electronic conductivity of TiO2 limit its capability of pseudocapacitive behavior with fast surface redox reaction. In this work, TiO2 quantum dots confined in 3-dimensional carbon framework have been synthesized by a facile process of reverse microemulsion method combined with heat treatment. The obtained composites effectively combine electrochemical redox with surface pseudocapacitive, showing excellent electrochemical properties. An ultra-high discharge capacity of 370.5 mAh/g can be retained after 200 cycles at a current density of 0.1 A/g. Ultra-long life extends to 10,000 cycles with an average capacity loss of as low as 0.00314% per cycle can be obtained at a high current density of 5.0 A/g, due to the high pesudocapacitance contribution of fast surface redox reaction. Furthermore, the practice application of the obtained electrode is also investigated in a full cell with LiCoO2 as the cathode and a high capacity retention of 93.5% is maintained after 100 cycles at the current density of 0.1 A/g.

A three-dimensional crosslinked chitosan sulfate network binder for high-performance Li–S batteries

Abstract Poor cycling performance caused by the shuttle effect of polysulfides is the main obstacle in the development of advanced lithium–sulfur (Li–S) batteries. Functional polymer binders with polar groups can effectively adsorb polysulfides chemically, thereby suppressing the shuttle effect. Herein, a robust three-dimensional crosslinked polymer network, which demonstrates excellent mechanical property and strong affinity for polysulfides, is prepared by the aldimine condensation and coordination reactions. The crosslinked chitosan sulfate network (CCSN) significantly enhances the cycling performance and rate capability of the sulfur cathode. The CCSN-based sulfur cathode exhibits a high initial discharge capacity of 824 mAh g-1 with only 0.082% average capacity loss per cycle at 1 C. At a high rate of 4 C, the cathode exhibits a high capacity retention of 84.8% after 300 cycles. Moreover, the CCSN-based sulfur cathode exhibits an excellent cycling performance at a high sulfur loading of 2.5 mg cm-2, which indicates the excellent mechanical strength and binding performance of the CCSN binder for high-energy density Li–S batteries. This study demonstrates a viable approach for developing high-performance Li–S batteries for practical application.