Co-intercalation reactions make graphite as promising anodes for sodium ion batteries, however, the high redox potentials significantly lower the energy density. Herein, we investigate the factors ...that influence the co-intercalation potential of graphite and find that the tuning of the voltage as large as 0.38 V is achievable by adjusting the relative stability of ternary graphite intercalation compounds and the solvent activity in electrolytes. The feasibility of graphite anode in sodium ion batteries is confirmed in conjunction with Na
VPO
F
cathodes by using the optimal electrolyte. The sodium ion battery delivers an improved voltage of 3.1 V, a high power density of 3863 W kg
, negligible temperature dependency of energy/power densities and an extremely low capacity fading rate of 0.007% per cycle over 1000 cycles, which are among the best thus far reported for sodium ion full cells, making it a competitive choice in large-scale energy storage systems.
A look at rechargeable lithium and sodium ion batteries is presented. The principles of lithium and sodium ion batteries are among the topics discussed.
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IJS, KILJ, NUK, PNG, UL, UM
Anatase TiO2 is considered as one of the promising anodes for sodium‐ion batteries because of its large sodium storage capacities with potentially low cost. However, the precise reaction mechanisms ...and the interplay between surface properties and electrochemical performance are still not elucidated. Using multimethod analyses, it is herein demonstrated that the TiO2 electrode undergoes amorphization during the first sodiation and the amorphous phase exhibits pseudocapacitive sodium storage behaviors in subsequent cycles. It is also shown that the pseudocapacitive sodium storage performance is sensitive to the nature of solid electrolyte interphase (SEI) layers. For the first time, it is found that ether‐based electrolytes enable the formation of thin (≈2.5 nm) and robust SEI layers, in contrast to the thick (≈10 nm) and growing SEI from conventional carbonate‐based electrolytes. First principle calculations suggest that the higher lowest unoccupied molecular orbital energies of ether solvents/ion complexes are responsible for the difference. TiO2 electrodes in ether‐based electrolyte present an impressive capacity of 192 mAh g−1 at 0.1 A g−1 after 500 cycles, much higher than that in carbonate‐based electrolyte. This work offers the clarified picture of electrochemical sodiation mechanisms of anatase TiO2 and guides on strategies about interfacial control for high performance anodes.
A thin and robust solid electrolyte interphase formed on a TiO2 surface that is enabled by using ether electrodes is demonstrated in Na‐ion batteries. This electrolyte/electrolyte interface, which is superior to conventional carbonate electrolyte, results in largely different electrochemical performances. The fundamental origin of the difference is unveiled through the combination of intensive experimental characterizations and first principles calculations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Adjuvant chemotherapy after surgery improves survival of patients with stage II–III, resectable gastric cancer. However, the overall survival benefit observed after adjuvant chemotherapy is moderate, ...suggesting that not all patients with resectable gastric cancer treated with adjuvant chemotherapy benefit from it. We aimed to develop and validate a predictive test for adjuvant chemotherapy response in patients with resectable, stage II–III gastric cancer.
In this multi-cohort, retrospective study, we developed through a multi-step strategy a predictive test consisting of two rule-based classifier algorithms with predictive value for adjuvant chemotherapy response and prognosis. Exploratory bioinformatics analyses identified biologically relevant candidate genes in gastric cancer transcriptome datasets. In the discovery analysis, a four-gene, real-time RT-PCR assay was developed and analytically validated in formalin-fixed, paraffin-embedded (FFPE) tumour tissues from an internal cohort of 307 patients with stage II–III gastric cancer treated at the Yonsei Cancer Center with D2 gastrectomy plus adjuvant fluorouracil-based chemotherapy (n=193) or surgery alone (n=114). The same internal cohort was used to evaluate the prognostic and chemotherapy response predictive value of the single patient classifier genes using associations with 5-year overall survival. The results were validated with a subset (n=625) of FFPE tumour samples from an independent cohort of patients treated in the CLASSIC trial (NCT00411229), who received D2 gastrectomy plus capecitabine and oxaliplatin chemotherapy (n=323) or surgery alone (n=302). The primary endpoint was 5-year overall survival.
We identified four classifier genes related to relevant gastric cancer features (GZMB, WARS, SFRP4, and CDX1) that formed the single patient classifier assay. In the validation cohort, the prognostic single patient classifier (based on the expression of GZMB, WARS, and SFRP4) identified 79 (13%) of 625 patients as low risk, 296 (47%) as intermediate risk, and 250 (40%) as high risk, and 5-year overall survival for these groups was 83·2% (95% CI 75·2–92·0), 74·8% (69·9–80·1), and 66·0% (60·1–72·4), respectively (p=0·012). The predictive single patient classifier (based on the expression of GZMB, WARS, and CDX1) assigned 281 (45%) of 625 patients in the validation cohort to the chemotherapy-benefit group and 344 (55%) to the no-benefit group. In the predicted chemotherapy-benefit group, 5-year overall survival was significantly improved in those patients who had received adjuvant chemotherapy after surgery compared with those who received surgery only (80% 95% CI 73·5–87·1 vs 64·5% 56·8–73·3; univariate hazard ratio 0·47 95% CI 0·30–0·75, p=0·0015), whereas no such improvement in 5-year overall survival was observed in the no-benefit group (72·9% 66·5–79·9 in patients who received chemotherapy plus surgery vs 72·5% 65·8–79·9 in patients who only had surgery; 0·93 0·62–1·38, p=0·71). The predictive single patient classifier groups (chemotherapy benefit vs no-benefit) could predict adjuvant chemotherapy benefit in terms of 5-year overall survival in the validation cohort (pinteraction=0·036 in univariate analysis). Similar results were obtained in the internal evaluation cohort.
The single patient classifiers validated in this study provide clinically important prognostic information independent of standard risk-stratification methods and predicted chemotherapy response after surgery in two independent cohorts of patients with resectable, stage II–III gastric cancer. The single patient classifiers could complement TNM staging to optimise decision making in patients with resectable gastric cancer who are eligible for adjuvant chemotherapy after surgery. Further validation of these results in prospective studies is warranted.
Ministry of ICT and Future Planning; Ministry of Trade, Industry, and Energy; and Ministry of Health and Welfare.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Lithium–oxygen chemistry offers the highest energy density for a rechargeable system as a “lithium–air battery”. Most studies of lithium–air batteries have focused on demonstrating battery operations ...in pure oxygen conditions; such a battery should technically be described as a “lithium–dioxygen battery”. Consequently, the next step for the lithium–“air” battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO2 is of particular interest because of its high solubility in organic solvents and it can react actively with O2 –•, which is the key intermediate species in Li–O2 battery reactions. In this work, we investigated the reaction mechanisms in the Li–O2/CO2 cell under various electrolyte conditions using quantum mechanical simulations combined with experimental verification. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect. Thus, a low dielectric electrolyte tends to primarily form Li2O2, while a high dielectric electrolyte is effective in electrochemically activating CO2, yielding only Li2CO3. Most surprisingly, we further discovered that a high dielectric medium such as DMSO can result in the reversible reaction of Li2CO3 over multiple cycles. We believe that the current mechanistic understanding of the chemistry of CO2 in a Li–air cell and the interplay of CO2 with electrolyte solvation will provide an important guideline for developing Li–air batteries. Furthermore, the possibility for a rechargeable Li–O2/CO2 battery based on Li2CO3 may have merits in enhancing cyclability by minimizing side reactions.
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IJS, KILJ, NUK, PNG, UL, UM
Cobalt‐free layered lithium‐rich nickel manganese oxides, LiLixNiyMn1−x−yO2 (LLNMO), are promising positive electrode materials for lithium rechargeable batteries because of their high energy density ...and low materials cost. However, substantial voltage decay is inevitable upon electrochemical cycling, which makes this class of materials less practical. It has been proposed that undesirable voltage decay is linked to irreversible structural rearrangement involving irreversible oxygen loss and cation migration. Herein, the authors demonstrate that the voltage decay of the electrode is correlated to Mn4+/Mn3+ redox activation and subsequent cation disordering, which can be remarkably suppressed via simple compositional tuning to induce the formation of Ni3+ in the pristine material. By implementing our new strategy, the Mn4+/Mn3+ reduction is subdued by an alternative redox reaction involving the use of pristine Ni3+ as a redox buffer, which has been designed to be widened from Ni3+/Ni4+ to Ni2+/Ni4+, without compensation for the capacity in principle. Negligible change in the voltage profile of modified LLNMO is observed upon extended cycling, and manganese migration into the lithium layer is significantly suppressed. Based on these findings, we propose a general strategy to suppress the voltage decay of Mn‐containing lithium‐rich oxides to achieve long‐lasting high energy density from this class of materials.
A novel strategy to suppress the voltage decay in layered lithium‐rich nickel manganese oxides is demonstrated using a Ni redox buffer. A substitution of Mn with Ni in lithium‐rich nickel manganese oxides results in the deactivation of Mn reduction, which is compensated by Ni redox reaction. Mn deactivation reduces the undesirable phase transformation, eventually leading to the suppression of the voltage decay.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
LiNiO2 (LNO) is a promising cathode material for next‐generation Li‐ion batteries due to its exceptionally high capacity and cobalt‐free composition that enables more sustainable and ethical ...large‐scale manufacturing. However, its poor cycle life at high operating voltages over 4.1 V impedes its practical use, thus motivating efforts to elucidate and mitigate LiNiO2 degradation mechanisms at high states of charge. Here, a multiscale exploration of high‐voltage degradation cascades associated with oxygen stacking chemistry in cobalt‐free LiNiO2, is presented. Lattice oxygen loss is found to play a critical role in the local O3–O1 stacking transition at high states of charge, which subsequently leads to Ni‐ion migration and irreversible stacking faults during cycling. This undesirable atomic‐scale structural evolution accelerates microscale electrochemical creep, cracking, and even bending of layers, ultimately resulting in macroscopic mechanical degradation of LNO particles. By employing a graphene‐based hermetic surface coating, oxygen loss is attenuated in LNO at high states of charge, which suppresses the initiation of the degradation cascade and thus substantially improves the high‐voltage capacity retention of LNO. Overall, this study provides mechanistic insight into the high‐voltage degradation of LNO, which will inform ongoing efforts to employ cobalt‐free cathodes in Li‐ion battery technology.
Lattice oxygen loss is found to play a critical role in the O3–O1 stacking transition in cobalt‐free LiNiO2 lithium‐ion battery cathodes, which subsequently induces Ni‐ion migration and irreversible stacking faults, microscale creep, cracking, and even bending of layers after high‐voltage cycling. By suppressing oxygen evolution, hermetic graphene coatings arrest this degradation cascade, resulting in substantially improved high‐voltage capacity retention.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The design and synthesis of low‐cost electrocatalysts with high catalytic activity and long‐term stability is a challenging task. This study utilizes a combination of electronic tuning and surface ...reconstruction to synthesize a ternary layered double hydroxide (LDH)/phosphide (P−NiCuFe−LDH) hierarchical‐structure catalyst that improves the kinetics of the hydrogen/oxygen evolution reactions in water electrolysis by facilitating the thermodynamically limited reaction pathways. Spectroscopic analyses indicate synergistic electronic interactions among the metal atoms in the LDH and phosphide layers via the P‐bridge effect. This cross‐layer interaction optimizes the electron transport pathways and reaction kinetics, enabling the proposed hierarchical electrocatalyst to exhibit high intrinsic activity. Theoretical calculations confirm the configuration of the cross‐phase bridges and elucidate the origin of the enhanced electrocatalytic effect of P−NiCuFe−LDH. For overall water splitting, the P−NiCuFe0.06−LDH || P−NiCuFe0.06−LDH system requires only 1.517 V to attain a current density of 10 mA cm−2. The P−O‐containing surface (generated in situ during water electrolysis) prevents metal‐ion leaching and endows P−NiCuFe−LDH with excellent operational stability; as demonstrated by the continuous long‐term stability test over 1000 h with negligible performance degradation. This study provides important insights into the design of rational hierarchical structures for a wide range of applications beyond water splitting.
A well‐designed hierarchical catalyst, P−NiCuFe−LDH, is constructed by structural transformation and surface reconstruction, which enhance the electron transport efficacy and reaction kinetics due to the synergistic electronic interactions via the P‐bridge effect. The excellent overall water splitting performance with a low cell voltage of 1.517 V at 10 mA cm−2 is shown by the proposed catalyst, along with remarkable operational stability over 1000 h.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Full solar light spectrum active Bi2S3@CdS@RGO photocatalyst was prepared for the first time.•Heterostructure endowed a high interface area and superb photocatalytic activity over ...solely counterparts.•High Cr(VI) reduction and H2O2 production rates are achieved under illumination.•Both experimental and DFT calculations reveal the photocatalysis mechanism.
Heterostructure-based photocatalysis offers significant potential for developing ultraviolet–visible (UV–Vis) to near-infrared (NIR) light-responsive catalysts with abundant beneficial physicochemical properties to boost environmental remediation upon solar-light irradiation. In this study, for the first time a novel ternary heterostructure photocatalysts containing Bi2S3@CdS@RGO (BCG) were rationally constructed using the hydrothermal approach. The resultant ternary composite with 5 wt% of CdS and 20 wt% of reduced graphene oxide (RGO) contents (BCG-5) was adopted as an optimal sample for photo-reduction of Cr(VI) under simulated solar-light irradiation. The apparent rate constant of the photo-reduction process over BCG-5 was ~ 13, 4, and 3 times higher than those of Bi2S3, CdS, and BC-5, respectively, within 150 min. The enhanced photocatalytic activity of ternary composite could be linked predominantly to the formation of heterostructural, synergistic behavior between the components, hierarchical morphology, the formation of n-n type high-low junctions, efficient interfacial charge-transfer capability, large specific surface area, full-spectrum light-absorption, and outstanding photo-stability. Electron spin resonance and reactive radical-scavenging results demonstrated that the hydroxyl and superoxide active species were primarily responsible for Cr(VI) removal. Furthermore, the photocatalytic activity of BCG-5, as an optimal sample, was further assessed regarding the photocatalytic production of H2O2, with 1.37 and 15.14 times higher efficiency than binary and bare samples, respectively. Assisted by the density functional theory calculations, ultraviolet photoelectron spectroscopy analyses, the charge-carriers pathway and possible photocatalytic mechanism were systematically discussed in S-scheme heterojunction. We expect that our findings will open new horizons for significant applications of bismuth-rich-based heterostructures under both visible- and NIR-light irradiation to address environmental and energy issues.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Recent discovery of high-concentration electrolyte systems has opened a new avenue toward the high-voltage, safe, and low-cost aqueous rechargeable batteries. However, the need for ...generally high-cost organic solutes in the high-concentration electrolyte has become another major obstacle. Herein, we revisited all the commonly used low-cost solutes for high-concentration system and discovered that the use of NaClO4 solute effectively results in a wide electrochemical stability window by suppressing water decomposition and induces stable solid-electrolyte interphase (SEI) layer formation without involving the reduction of salt anions. The SEI layer, composed of Na2CO3 and NaO compounds including NaOH, guarantees the excellent electrochemical storage stability of the full-cell composed of Na4Fe3(PO4)2(P2O7) cathode and NaTi2(PO4)3 anode for the extended period of time. This new class of electrolyte systems provides remarkable cycle stability and a coulombic efficiency of ∼99% at 1C for over 200 cycles, which outperforms the state-of-the-art super-concentrated systems based on NaCF3SO3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP