Dual extended Kalman filter for state of charge estimation of lithium–sulfur batteries

Lithium-Sulfur is a promising technology for the next generation of batteries and research efforts for early-stage prototype implementation increased in recent years. For the development of a suitable Battery Management System, a state estimator is required; however, lithium-sulfur behavior presents a large non-observable region that may difficult the convergence of the state estimation algorithm leading to large errors or even instability. A dual Extended Kalman Filter is proposed to circumvent the non-observability region. This objective is achieved by combining a parameter estimation algorithm with a cell model that includes non-linear behavior such as self-discharge and cell degradation. The resulting dual Kalman filter is applied to lithium–sulfur batteries to estimate their State-of-Charge incorporating the effects of degradation, temperature, and self-discharge deviations.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.b - Per a 2030, ampliar la infraestructura i millorar la tecnologia per tal d’oferir serveis d’energia moderns i sos­tenibles per a tots els països en desenvolupament, en particular els països menys avançats, els petits estats insulars en desenvolupament i els països en desenvolupament sense litoral, d’acord amb els programes de suport respectiusObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (published version

Tubular CoFeP@CN as a Mott–Schottky catalyst with multiple adsorption sites for robust lithium-sulfur batteries

The shuttle effect and the sluggish reaction kinetics of lithium polysulfide (LiPS) seriously compromise the performance of lithium–sulfur batteries (LSBs). To overcome these limitations and enable the fabrication of robust LSBs, here the use of a Mott–Schottky catalyst based on bimetallic phos- phide CoFeP nanocrystals supported on carbon nitride tubular nanostruc- tures as sulfur hosts is proposed. Theoretical calculations and experimental data confirm that CoFeP@CN composites are characterized by a suitable electronic structure and charge rearrangement that allows them to act as a Mott–Schottky catalyst to accelerate LiPS conversion. In addition, the tubular geometry of CoFeP@CN composites facilitates the diffusion of Li ions, accommodates volume change during the reaction, and offers abundant lithi- ophilic/sulfiphilic sites to effectively trap soluble LiPS. Therefore, S@CoFeP@ CN electrodes deliver a superior rate performance of 630 mAh g-1 at 5 C, and remarkable cycling stability with 90.44% capacity retention over 700 cycles. Coin cells with high sulfur loading, 4.1 mg cm-2, and pouch cells with 0.1 Ah capacities are further produced to validate their superior cycling stability. In addition, it is demonstrated here that CoFeP@CN hosts greatly alleviate the often overlooked issues of low energy efficiency and serious self-discharging in LSBs.Peer ReviewedPostprint (author's final draft

Exploring the nanoscale origin of performance enhancement in Li1.1_{1.1}Ni0.35_{0.35}Mn0.55_{0.55}O2_2 batteries due to chemical doping

Despite significant potential as energy storage materials for electric vehicles due to their combination of high energy density per unit cost and reduced environmental and ethical concerns, Co-free lithium ion batteries based off layered Mn oxides presently lack the longevity and stability of their Co-containing counterparts. Here, we demonstrate a reduction in this performance gap via chemical doping, with Li$_{1.1}$Ni$_{0.35}$Mn$_{0.55}$O$_2$ achieving an initial discharge capacity of 159 mAhg$^{-1}$ at C/3 rate and a corresponding capacity retention of 94.3% after 150 cycles. We subsequently explore the nanoscale origins of this improvement through a combination of advanced diffraction, spectroscopy, and electron microscopy techniques, finding that optimized doping profiles lead to an improved structural and chemical compatibility between the two constituent sub-phases that characterize the layered Mn oxide system, resulting in the formation of unobstructed lithium ion pathways between them. We also directly observe a structural stabilization effect of the host compound near the surface using aberration corrected scanning transmission electron microscopy and integrated differential phase contrast imaging.Comment: 20 pages, 8 figure

NbSe2 meets C2N: a 2D-2D heterostructure catalysts as multifunctional polysulfide mediator in ultra-long-life lithium–sulfur batteries

The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPS) hamper the practical application of lithium–sulfur batteries (LSBs). Toward overcoming these limitations, herein an in situ grown C2N@NbSe2 heterostructure is presented with remarkable specific surface area, as a Li–S catalyst and LiPS absorber. Density functional theory (DFT) calculations and experimental results comprehensively demonstrate that C2N@NbSe2 is characterized by a suitable electronic structure and charge rearrangement that strongly accelerates the LiPS electrocatalytic conversion. In addition, heterostructured C2N@NbSe2 strongly interacts with LiPS species, confining them at the cathode. As a result, LSBs cathodes based on C2N@NbSe2/S exhibit a high initial capacity of 1545 mAh g-1 at 0.1 C. Even more excitingly, C2N@NbSe2/S cathodes are characterized by impressive cycling stability with only 0.012% capacity decay per cycle after 2000 cycles at 3 C. Even at a sulfur loading of 5.6 mg cm-2, a high areal capacity of 5.65 mAh cm-2 is delivered. These results demonstrate that C2N@NbSe2 heterostructures can act as multifunctional polysulfide mediators to chemically adsorb LiPS, accelerate Li-ion diffusion, chemically catalyze LiPS conversion, and lower the energy barrier for Li2S precipitation/decomposition, realizing the “adsorption-diffusion-conversion” of polysulfides.Award-winningPostprint (author's final draft

New Opportunities for Air Cathode Batteries; in-Situ Neutron Diffraction Measurements

Batteries with air electrodes are gaining interest as Energy Storage Systems (ESSs) for Electrical Vehicles (EVs) because of their high specific energy density. The electrochemical performance of these batteries is limited by the metallic electrode, which suffers structural transformations and corrosion during cycling that reduces the cycle life of the battery. In this context, relevant information on the discharge products may be obtained by in-situ neutron diffraction, a suitable technique to study electrodes that contain light elements or near neighbor elements in the periodic table. Case studies of MH-air and Fe-air batteries are highlighted

Atomically dispersed Fe in a C2N based catalyst as a sulfur host for efficient lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, C2N, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X-ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/C2N catalyst. As a result, Fe/C2N-based cathodes demonstrate significantly improved rate performance and long-term cycling stability. Fe/C2N-based cathodes display initial capacities up to 1540 mAh g-1 at 0.1 C and 678.7 mAh g-1 at 5 C, while retaining 496.5 mAh g-1 after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm-2, they deliver remarkable specific capacity retention of 587 mAh g-1 after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high-performance cathodes based on atomically dispersed catalysts for LSBs.Peer ReviewedPostprint (author's final draft

Tubular CoFeP@CN as a Mott–Schottky Catalyst with Multiple Adsorption Sites for Robust Lithium−Sulfur Batteries

The shuttle effect and the sluggish reaction kinetics of lithium polysulfide (LiPS) seriously compromise the performance of lithium–sulfur batteries (LSBs). To overcome these limitations and enable the fabrication of robust LSBs, here the use of a Mott–Schottky catalyst based on bimetallic phosphide CoFeP nanocrystals supported on carbon nitride tubular nanostructures as sulfur hosts is proposed. Theoretical calculations and experimental data confirm that CoFeP@CN composites are characterized by a suitable electronic structure and charge rearrangement that allows them to act as a Mott–Schottky catalyst to accelerate LiPS conversion. In addition, the tubular geometry of CoFeP@CN composites facilitates the diffusion of Li ions, accommodates volume change during the reaction, and offers abundant lithiophilic/sulfiphilic sites to effectively trap soluble LiPS. Therefore, S@CoFeP@CN electrodes deliver a superior rate performance of 630 mAh g at 5 C, and remarkable cycling stability with 90.44% capacity retention over 700 cycles. Coin cells with high sulfur loading, 4.1 mg cm, and pouch cells with 0.1 Ah capacities are further produced to validate their superior cycling stability. In addition, it is demonstrated here that CoFeP@CN hosts greatly alleviate the often overlooked issues of low energy efficiency and serious self-discharging in LSBs.This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project ENE2016-77798-C4-3-R, and ENE2017-85087-C3. C.Q.Z., R.F.D., K.X., D.W.Y., T.Z., and X.W. thank the China Scholarship Council for the scholarship support. The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and was funded by the CERCA Programme/Generalitat de Catalunya. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program

Rational design of MXene/activated carbon/polyoxometalate triple hybrid electrodes with enhanced capacitance for organic-electrolyte supercapacitors

Altres ajuts: ICN2 and IREC are funded by the CERCA programme / Generalitat de Catalunya, and ICN2. This work has been carried out within the framework of doctoral program (PhD) of Material Science (Department of Physics) of Universitat Autònoma de Barcelona (UAB).We report a triple hybrid electrode (MXene/activated carbon (AC)/polyoxometalates (POMs)) combining the merits of three materials: MXene (high volumetric capacitance), AC (high gravimetric capacitance) and Phosphotungstate (fast redox). Phosphotungstic acid (HPW12) and tetraethylammonium phosphotungstate (TEAPW12) were the two POMs used to prepare MXene/AC/POMs triple hybrids. MXene/AC/TEAPW12 outperformed MXene/AC/HPW12 in 1 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile. Nano-dispersion of POMs facilitates charge storage through surface capacitive processes (91% at 2 mV s). MXene/AC/TEAPW12 delivered significantly higher gravimetric capacitance (87F g at 1 mV s) than MXene (40F g at 1 mV s) in the same organic electrolyte, without sacrificing much volumetric capacitance (less than 10%). The gravimetric capacitance of the triple hybrid was similar to that of MXene/AC, whereas its volumetric capacitance was 1.5 times higher. Replacing TEA cations with 1-ethyl-3-methylimidazolium cations (EMIM), the capacitance improved by 21%. Coupled with AC positive electrodes in an asymmetric cell, MXene/AC/TEAPW12 delivered 4.6 times higher gravimetric energy density and 3.5 times higher volumetric energy density than a similar MXene asymmetric cell at relatively high-power densities. This study proves that MXene/AC/TEAPW12 combines the merits and compensates for the demerits of each component and is a promising electrode material for organic-electrolyte supercapacitors

Atomically dispersed Fe in a C2N based catalyst as a sulfur host for efficient lithium-sulfur batteries

Altres ajuts: ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. J.L. is a Serra Húnter Fellow and is grateful to ICREA Academia program.Lithium-sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, CN, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X-ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/CN catalyst. As a result, Fe/CN-based cathodes demonstrate significantly improved rate performance and long-term cycling stability. Fe/CN-based cathodes display initial capacities up to 1540 mAh g at 0.1 C and 678.7 mAh g at 5 C, while retaining 496.5 mAh g after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm, they deliver remarkable specific capacity retention of 587 mAh g after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high-performance cathodes based on atomically dispersed catalysts for LSBs

Identifying the Role of the Cationic Geometric Configuration in Spinel Catalysts for Polysulfide Conversion in Sodium-Sulfur Batteries

An AB2X4 spinel structure, with tetrahedral A and octahedral B sites, is a paradigmatic class of catalysts with several possible geometric configurations and numerous applications, including polysulfide conversion in metal-sulfur batteries. Nonetheless, the influence of the geometric configuration and composition on the mechanisms of catalysis and the precise manner in which spinel catalysts facilitate the conversion of polysulfides remain unknown. To enable controlled exposure of single active configurations, herein, Cotd2+ and Cooh3+ in Co3O4 catalysts for sodium polysulfide conversion are in large part replaced by Fetd2+ and Feoh3+, respectively, generating FeCo2O4 and CoFe2O4. Through an examination of electrochemical activation energies, the characterization of symmetric cells, and theoretical calculations, we determine that Cooh3+ serves as the active site for the breaking of S-S bonds, while Cotd2+ functions as the active site for the formation of S-Na bonds. The current study underlines the subtle relationship between activity and geometric configurations of spinel catalysts, providing unique insights for the rational development of improved catalysts by optimizing their atomic geometric configuration.This work was supported by the Innovation fund for small and medium-sized Enterprises in Gansu Province (No. 22CX3JA006), Lanzhou Talent Innovation and Entrepreneurship Project (No. 2022-2-81), National Natural Science Foundation of China (Grant Nos. 61801200), and partially by the Fundamental Research Funds for the Central Universities (Grant No.: lzujbky-2021-it33). J.S. Li acknowledges financial support from the Natural Science Foundation of Sichuan province (2022NSFSC1229). ICN2 acknowledges funding from Generalitat de Catalunya 2021SGR00457. This study is part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat de Catalunya. The authors thank the support from the project NANOGEN (PID2020-116093RB-C43), funded by MCIN/AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”, by the “European Union”. ICN2 is supported by the Severo Ochoa program from Spanish MCIN/AEI (Grant No.: CEX2021-001214-S) and is funded by the CERCA Programme/Generalitat de Catalunya. AGM has received funding from Grant RYC2021-033479-I funded by MCIN/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. L.B. thanks the Ministry of Science and Innovation of Spain through the OXISHOT project (PID2021-128410OB-I00). ICN2 acknowledges funding from Project IU16-014206 (METCAM-FIB) from Generalitat de Catalunya and by “ERDF A way of making Europe”, by the European Union.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe