NA Cells Research Articles

Revealing sodium storage mechanism in lithium titanium phosphate: Combined experimental and theoretical study

We investigate a LiTi2(PO4)3–carbon composite (LTP-C) with a sodium superionic conductor (NASICON)-type structure as a potential electrode material for sodium storage. Operando X-ray diffraction and ex situ X-ray absorption spectroscopic analyses reveal that repetitive electrochemical reduction (discharge) and oxidation (charge) between 1.2 and 3.1 V results in a two-phase redox process associated with the Ti4+/3+ redox couple. The rearrangement of the alkali sites during discharge/charge is investigated using first-principles calculations and Rietveld refinement. Using first-principles calculations, we verify the possibility of ion exchange from Li+ to Na+ in LiTi2(PO4)3 in Na cells as well as various theoretical electrochemical properties of LiNa2Ti2(PO4)3 and Na3Ti2(PO4)3. Notably, the sodiated LTP-C exhibits a stable cycle life for over 300 cycles at 0.5C and for over 1000 cycles at 5C with capacity retention of 99% and 94%, respectively.

Deficiency of Dietary Fiber in Slc5a8-Null Mice Promotes Bacterial Dysbiosis and Alters Colonic Epithelial Transcriptome towards Proinflammatory Milieu.

Inflammatory bowel disease (IBD) is characterized by chronic inflammation in the intestinal tract due to disruption of the symbiotic relationship between the host immune system and microbiota. Various factors alter the gut microbiota which lead to dysbiosis; in particular, diet and dietary fibers constitute important determinants. Dietary fiber protects against IBD; bacteria ferment these dietary fibers in colon and generate short-chain fatty acids (SCFAs), which mediate the anti-inflammatory actions of dietary fibers. SLC5A8 is a high-affinity transporter in the apical membrane of colonic epithelium which mediates the entry of SCFAs from the lumen into cells in Na+-coupled manner. Due to the unique transport kinetics, the function of the transporter becomes important only under conditions of low dietary fiber intake. Here, we have examined the impact of dietary fiber deficiency on luminal microbial composition and transcriptomic profile in colonic epithelium in wild-type (WT) and Slc5a8-null (KO) mice. We fed WT and KO mice with fiber-containing diet (FC-diet) or fiber-free diet (FF-diet) and analyzed the luminal bacterial composition by sequencing 16S rRNA gene in feces. Interestingly, results showed significant differences in the microbial community depending on dietary fiber content and on the presence or absence of Slc5a8. There were also marked differences in the transcriptomic profile of the colonic epithelium depending on the dietary fiber content and on the presence or absence of Slc5a8. We conclude that absence of fiber in diet in KO mice causes bacterial dysbiosis and alters gene expression in the colon that is conducive for inflammation.

Loss of Asxl1 Cooperates with Oncogenic Nras to Drive CMML Progression

Chronic myelomonocytic leukemia (CMML) belongs to the group of "mixed myelodysplastic/myeloproliferative neoplasm". There is currently no effective chemotherapy to treat CMML. Approximately 30% of CMML cases evolve to acute myeloid leukemia (AML) soon after their initial diagnosis, contributing to the poor prognosis of CMML patients. Ras pathway genes are frequently mutated in CMML patients (NRAS:11%; CBL:10%; KRAS:8%). Our whole exome sequencing of CMML patient samples and targeted sequencing of CMML patient-derived myeloid colonies showed that oncogenic NRAS could serve as an initiating or progression mutation. Consistent with human genetics, all the oncogenic Nras mice we and others characterized (NrasG12D/+, NrasG12D/G12D, and NrasQ61R/+), develop myeloproliferative (MP)-CMML like phenotypes.However, oncogenic NRAS alone is insufficient to drive CMML progression or transformation to AML. Additional sex combs-like 1 (ASXL1) is a human homolog of fly Asx. Mutations in ASXL1are predominantly nonsense and frequently identified in all myeloid malignancies (e.g. 40% in CMML). ASXL1mutations predict inferior overall survival in univariable analysis in multiple large CMML cohort studies and are significantly associated with NRASmutations in CMML patients. Therefore, we hypothesize that loss of Asxl1 cooperates with oncogenic Nrasto drive CMML progression. To test our hypothesis, we used Vav-Cre to drive oncogenic Nras expression and/or Asxl1 deletion in hematopoietic system. We refer these mice as NrasG12D/+, Asxl1-/-and NrasG12D/+;Asxl1-/-(NA) mice. Consistent with the literature, Asxl1-/-mice are normal at 6-week old. NrasG12D/+ mice showed mild CMML-like phenotypes, including enlarged spleen, increased white blood cell and monocyte counts, and expanded LSKs (Lin-Sca-1+c-Kit+) and myeloid progenitors (MPs). Compared to NrasG12D/+ mice, NA mice showed more sever phenotypes that were associated with hyperactivated ERK signaling in MPs at both basal level and upon GM-CSF stimulation. Our new NrasG12D/+mice developed a fully penetrant MP-CMML with the median survival of ~430 days. Loss of Asxl1 significantly shortened the median survival of NrasG12D/+ mice to 220 days. Half of NA mice displayed CMML transformation to AML. The transformed AML was serially transplantable to recipients. To investigate the mechanism(s) underlying NA-driven CMML/AML, we performed RNA-Seq analysis in Lin- c-Kit+BM cells from age-matched control, Asxl1-/-, NrasG12D/+, and moribund NA mice with CMML or AML phenotypes. We found 844 differentially expressed genes (DEG) in AML cells compared to control cells (FDR<0.05 and fold change>2). Among these genes, 341 are common between NA and published Nf1+/-;Asxl1+/-AML cells, including AP-1 complex genes (Jun, Junb, Jund and Fosb) that are crucial for malignant propagation in several AML subtypes. The remaining 503 genes are unique in NA AML, including Flt3, one of the mostly mutated genes in AML. These data suggest that our NA AML model demonstrates some distinct mechanisms from Nf1+/-;Asxl1+/-model. In-depth analysis of RNA-seq data is still ongoing. We also examined multiple histone marks using Western blot in BM cells of 6-week old mice. Our data showed that levels of H3K4me3, H3K4me1, and H3K27me3 were downregulated in Asxl1-/-cells, whereas H3K27Ac level was comparable to that of control cells. In contrast, H3K27Ac level was upregulated in NrasG12D/+and NA cells, while levels of H3K4me3, H3K4me1, and H3K27me3 were indistinguishable from those of control cells. BRD4 is a member of the BET family of bromodomain-containing proteins that binds to acetylated histones to activate gene transcription. Thus, we hypothesized that Ras/MEK/ERK signaling and BRD/BET are potential targets to inhibit AML progression. To test this hypothesis, we treated the AML cells and BMT recipients using trametinib (a MEK inhibitor approved by FDA to treat melanoma) and GSK525762 (a pan BET inhibitor under clinical development). We demonstrated thatcombined treatment significantly inhibited the growth of leukemia cells in vitro and prolonged the survival of recipients in vivo. It was more effective than single agent alone. Overall, we established a novel CMML/AML mouse model, which represents a significant group of CMML patients with poor prognosis. Our study provides a strong rational to treat these patients with combined MEK and BET inhibition. Disclosures Patnaik: Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

Unexpected intercalation-dominated potassium storage in WS2 as a potassium-ion battery anode

Unexpected intercalation-dominated process is observed during K+ insertion in WS2 in a voltage range of 0.01–3.0 V. This is different from the previously reported two-dimensional (2D) transition metal dichalcogenides that undergo a conversion reaction in a low voltage range when used as anodes in potassium-ion batteries. Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate the different ion storage mechanisms. The Na+ storage proceeds through intercalation and conversion reactions while the K+ storage is governed by an intercalation reaction. Owing to the reversible K+ intercalation in the van der Waals gaps, the WS2 anode exhibits a low decay rate of 0.07% per cycle, delivering a capacity of 103 mAh·g-1 after 100 cycles at 100 mA·g-1. It maintains 57% capacity at 800 mA·g-1 and shows stable cyclability up to 400 cycles at 500 mA·g-1. Kinetics study proves the facilitation of K+ transport is derived from the intercalation-dominated mechanism. Furthermore, the mechanism is verified by the density functional theory (DFT) calculations, showing that the progressive expansion of the interlayer space can account for the observed results.

Grain-boundary-resistance-less Na3SbS4-xSex solid electrolytes for all-solid-state sodium batteries

A nanoscaled Na3SbS3.75Se0.25 solid electrolyte with less grain-boundary resistance was synthesized using a liquid/solid fusion technology. The Na3SbS3.75Se0.25 solid electrolyte shows a high ionic conductivity of 4.03 × 10−3 S cm−1 at room temperature due to the significantly decreased amorphous phase in the electrolyte. Moreover, the small particle size of the solid electrolytes enhances the contact between solid electrolyte and electrode, reducing the interfacial contact resistance. As a result, FeS2/Na3SbS3.75Se0.25/Na all-solid-state sodium batteries achieve a high specific capacity of 140.6 mAh g−1 for 300 cycles at a high current of 500 mA g−1. In addition, FeS2/Na3SbS3.75Se0.25/Na cells also demonstrate a high rate-capacity of 365.3, 301.8, 210.1 and 96.0 mAh g−1 at current densities of 50, 300, 500 and 1000 mA g−1, respectively. The liquid/solid fusion technology is a unique synthesis strategy to develop superionic electrolytes for room temperature all-solid-state sodium secondary battery.

Li/Na Storage Properties of Disordered Carbons Synthesized by Mechanical Milling

Impact of structural disorder induced by mechanical milling on electrochemical properties of carbonaceous materials is systematically examined. Carbonaceous materials with different structural disorder are prepared by mechanical milling with different rotation speeds. Thus prepared carbons show sloping voltage profiles in Li/Na cells, which resemble those of soft carbons. The disordered carbon material prepared at 600 rpm shows a reversible capacity of >500 mA h g−1 in a Li cell. In addition, the disordered carbon also delivers 200 mA h g−1 in a Na cell with high Coulombic efficiency for continuous cycles. Heat treatment of the disordered carbon results in the formation of hard carbon with nanopores, and thus Li/Na storage properties are significantly changed.

Small Functional Molecules As Slurry Additives for Si-Alloy Coatings with CMC/SBR Binder

Si-alloy based anodes are attractive for use in Li-ion batteries because of their high volumetric capacity. Polyacrylic acid (PAA) [1] binder is often used in such anodes, which contains carboxyl groups that bind to alloy surfaces, maintaining electrode integrity and forming an artificial SEI layer [2]. Aromatic binders like PI can decompose during lithiation, forming a conductive carbon network [3]. However, these binders have disadvantageous for their practical use, including superhydrophilicity, in the case of PAA; and high irreversible capacity and the cost and use of NMP solvent, in the case of PI. Sodium carboxymethyl cellulose/styrene-butadiene rubber (CMC/SBR) is currently the binder system of choice for Li-ion cell makers. Enabling the use of CMC/SBR binders with alloys could enable wider implementation of alloy electrodes. In this work, several small molecule compounds containing carboxyl groups were evaluated as slurry additives. It was found that some slurry additives could significantly improve alloy cycle life in CMC/SBR coatings. Figure 1 shows the capacity retention versus cycle number for each slurry additive. Tremendous variations in capacity retention are observed for different additives. In particular, the addition of 5% sodium mellitate and sodium citrate resulted in a large increase in cycling performance of the CMC/SBR coating beyond even that of a coating with PAA binder. This work shows that the cycle life of alloy coatings using CMC/SBR binder can be improved by the use of small molecule slurry additives. This could help enable the use of alloy based electrodes in Li-ion batteries using practical binder systems. Reference s : [1] Magasinski, Alexandre, et al. "Toward efficient binders for Li-ion battery Si-based anodes: polyacrylic acid." ACS applied materials & interfaces 2.11 (2010): 3004-3010. [2] Chen, Hao, et al. "Exploring chemical, mechanical, and electrical functionalities of binders for advanced energy-storage devices." Chemical reviews 118.18 (2018): 8936-8982. [3] Wilkes, B. N., et al. "The electrochemical behavior of polyimide binders in Li and Na cells." Journal of The Electrochemical Society 163.3 (2016): A364-A372. Figure 1

Stabilizing NaCrO2 By Sodium Site Doping with Calcium

O3-type NaCrO2 is a promising cathode material as it offers decent energy density and is easy to synthesize from abundant elements. A capacity fade of ~20% in 50 cycles is usually observed for NaCrO2 in organic solvents [1–3]. Research regarding improving the capacity retention of NaCrO2 includes coating the NaCrO2 particle with carbon [1,2], or increasing grain boundary content by nanosizing the grains [3]. In this study, NaCrO2 was Na-site doped with calcium to improve cycling retention in Na cells. A series of [Na1-2xCax]CrO2 materials were synthesized using a solid state method. Figure 1(a) shows the XRD pattern and Rietveld refinement of [Na0.9Ca0.05]CrO2. A single O3 phase was obtained with no observable impurity. Figure 1(b) shows the capacity and coulombic efficiency versus cycle number for NaCrO2 and [Na0.9Ca0.05]CrO2 when cycled in the voltage range of 2 V – 3.6 V. Both materials have similar initial capacity, However the capacity retention of Na0.9Ca0.05CrO2 is significantly improved, compared to NaCrO2. The coulombic efficiency of Na0.9Ca0.05CrO2 is also constantly higher than NaCrO2. It is speculated that calcium substitution results in a more stable structure during sodium (de)intercalation. The effect of calcium substitution on structural changes during cycling and air-stability will be discussed. [1] J.J. Ding, Y.N. Zhou, Q. Sun, Z.W. Fu, Cycle Performance Improvement of NaCrO2 Cathode by Carbon Coating for Sodium Ion Batteries, Electrochem. Commun. 22 (2012) 85–88. [2] C.Y. Yu, J.S. Park, H.G. Jung, K.Y. Chung, D. Aurbach, Y.K. Sun, S.T. Myung, NaCrO2 Cathode for High-Rate Sodium-Ion Batteries, Energy Environ. Sci. 8 (2015) 2019–2026. [3] Y. Tsuchiya, A.M. Glushenkov, N. Yabuuchi, Effect of Nanosizing on Reversible Sodium Storage in a NaCrO2 Electrode, ACS Appl. Nano Mater. 1 (2018) 364–370. Figure 1

Na3FePO4CO3 as a cathode for hybrid-ion batteries—study of Na+/Li+ electrochemical exchange

The Na+/Li+ electrochemical exchange in Na3FePO4CO3 (NFPC) carbonophosphate is studied for the first time in a hybrid cell using Li metal anode and Li-based electrolyte. The resulting ion-exchanged product is investigated. It is shown that the complete substitution of Na for Li is not achieved. The Na+/Li+ electrochemical exchange does not cause noticeable structural changes in the mixed Na/Li iron carbonophosphate; the initial monoclinic structure is preserved. During the first few cycles, a concurrent insertion of the Li+ and Na+ ions occurs, which is changed for the predominant Li intercalation/de-intercalation subsequently. Discharge capacity of NFPC/C achieves 61 mAh g−1 at 1 C, which is superior to that in a Na cell; the operating voltage is about 0.3 V higher. The Li/Na intercalation kinetics in the in situ formed mixed Na/Li iron carbonophosphate exceeds the sodium intercalation kinetics for NFPC cycled in a Na cell (DA+ = 1 × 10−15 cm2 s−1).

(Invited) On the NaMeO2 (Me = 3d metal) for Na-Ion Batteries

Since the first report of NaMeO2 electrode about 40 years ago, the oxides have attracted much attention in battery researchers’ community particularly after 2010 because of their new chemistries different from LiMeO2 as well as abundant material-resources in the Earth [1-4]. Table 1 shows the variety of directly crystalizable oxides of A x MeO2s (A = Li, Na, and K) on 3d transition metal species. Clearly, Na x MeO2 crystalizes with a wider variety of 3d transition metals without Na/Me cation-mixing unlike Li/Me due to proper difference in ionic radii between Na+ and Me3+ ions [5-7]. The wide variety of 3d metals and crystal structures such as O3, P3, and P2 types including the distorted ones are found only in the Na system [5-7], unlike Li and K cases. Such structural variety gives us so wide selection of Na x MeO2 materials, which is highly attractive to develop high-performance positive electrode and to fine new electrochemical properties. Even if the same 3d transition metal is adopted in Li and Na systems, the electrochemical properties are often different from Na one in the batteries. For examples, O3-type LiCrO2 is electrochemically inactive in a Li cell, while O3-NaCrO2 delivers a reversible capacity of ca. 120 mAh g-1 with anomalously high thermal-stability in Na cell [8,9], which is also found in between O3-LiFeO2 and O3-NaFeO2 [10-12]. Our group has studied layered Na x MeO2 since 2005, and our achievements and recent progress on the layered oxides will be presented. Reference s : [1] N. Yabuuchi, K. Kubota, M. Dahbi and S. Komaba, Chem. Rev., 114, 11636 (2014). [2] M. Dahbi, K. Kubota, S. Komaba et al., Phys. Chem. Chem. Phys., 16, 15007 (2014). [3] K. Kubota and S. Komaba, J. Electrochem. Soc., 162, A2538 (2015). [4] K. Kubota, S. Komaba et al., Chem. Rec., 18, 459 (2018). [5] C. Delmas, C. Fouassier, and P. Hagenmuller, Mater. Res. Bull., 11, 1483 (1976). [6] K. Kubota, S. Komaba et al., MRS Bull., 39, 416 (2014). [7] K. Kubota, S. Komaba et al., Adv. Energy Mater., 8, 1703415 (2018). [8] S. Komaba et al., Electrochem. Commun., 12, 355 (2010), and J. Phys. Chem. C, 119, 166–175 (2015). [9] N. Yabuuchi, S. Komaba, et al., ACS Appl. Mater. Interfaces, 8, 32292−32299 (2016). [10] K. Ado, et al., J. Electrochem. Soc., 144, L177 (1997). [11] S. Okada, the 210th ECS Meet., Cancun, Mexico (2006). [12] N. Yabuuchi, S. Komaba et al., Electrochemistry, 80, 716 (2012). Figure 1

Stable Na Metal Anode Enabled by a Reinforced Multistructural SEI Layer

AbstractMetallic sodium (Na) is one of the most promising anode candidates for next‐generation secondary batteries. The development of Na metal batteries with a high energy density and low cost is desirable to meet the requirements of both portable and stationary electrical energy storage. Unfortunately, several problems caused by the unstable Na metal anode severely hinder the practical applications of these batteries. Here reported is a facile but effective methodology to form a multistructural interphase layer containing a sodium fluoride‐rich solid electrolyte interphase (SEI) and crisscrossed Na3Sb bars on the Na electrode surface. The reinforced Na‐alloy network and chemically/electrochemically complementary SEI formation greatly improve the interphase strength and Na+ conductivity. The well‐protected Na metal electrode in symmetric Na|Na cells is stable and dendrite‐free in the plating and stripping cycling processes with a negligible voltage divergence, even at a large current density of 5 mA cm−2 or with a high deposition capacity of 10 mAh cm−2. Moreover, this anode is especially compatible with different cathodes and demonstrates outstanding cycle performance in the full cells. It is believed that this approach provides a practical solution toward stable Na metal anodes and related battery systems.

Phenotypic Consequence of Rearranging the N Gene of RABV HEP-Flury.

Nucleoprotein (N) is a key element in rabies virus (RABV) replication. To further investigate the effect of N on RABV, we manipulated an infectious cDNA clone of the RABV HEP-Flury to rearrange the N gene from its wild-type position of 1 (N-P-M-G-L) to 2 (P-N-M-G-L), 3 (P-M-N-G-L), or 4 (P-M-G-N-L), using an approach that left the viral nucleotide sequence unaltered. Subsequently, viable viruses were recovered from each of the rearranged cDNA and examined for their gene expression levels, growth kinetics in cell culture, pathogenicity in suckling mice and protection in mice. The results showed that gene rearrangement decreased N mRNA transcription and vRNA replication. As a result, all viruses with rearranged genomes showed worse replication than that of rHEP-Flury in NA cells at a MOI of 0.01, but equivalent or slightly better replication levels at a MOI of 3. Consequently, the lethality in suckling mice infected with N4 was clearly attenuated compared with rHEP-Flury. However, the protection to mice was not enhanced. This study not only gives us insight into the understanding of the phenotype of RABV N gene rearrangement, but also helps with rabies vaccine candidate construction.

α-VPO4: A Novel Many Monovalent Ion Intercalation Anode Material for Metal-Ion Batteries.

In this paper, we report on a novel α-VPO4 phosphate adopting the α-CrPO4 type structure as a promising anode material for rechargeable metal-ion batteries. Obtained by heat treatment of a structurally related hydrothermally prepared KTiOPO4-type NH4VOPO4 precursor under reducing conditions, the α-VPO4 material appears stable in a wide temperature range and possesses an interesting "sponged" needle-like particle morphology. The electrochemical performance of α-VPO4 as the anode material was examined in Li-, Na-, and K-based cells. The carbon-coated α-VPO4/C composite exhibits 185, 110, and 37 mA h/g specific capacities respectively at the first discharge and around 120, 80, and 30 mA h/g at consecutive cycles at a C/10 rate. The considerable capacity drop after the first cycle in Li and Na cells is presumably due to irreversible alkali ion consumption taking place upon alkali-ion de/insertion. The EDX analysis of the recovered electrodes revealed an uptake of ∼23% of Na after the first discharge with significant cell parameter alteration validated by operando XRD measurements. In contrast to the known β-VPO4 anode materials, both Li and Na de/insertion into the new α-VPO4 proceed via an intercalation mechanism with the parent structural framework preserved but not via a conversion mechanism. The dimensionality of alkali-ion migration pathways and diffusion energy barriers was analyzed by the BVEL approach. Na-ion diffusion coefficients measured by the potentiostatic intermittent titration technique are in the range of (0.3-1.0)·10-10 cm2/s, anticipating α-VPO4 as a prospective high-power anode material for Na-ion batteries.

Impact of Na2MoO4 nanolayers autogenously formed on tunnel-type Na0.44MnO2

The Na2MoO4 coating layer has multiple functionalities on tunnel-type Na0.44MnO2, providing electrical conductivity, scavenging HF, and providing surface protection that leads to excellent electrode performance in Na cells.

High-Rate Nanostructured Pyrite Cathodes Enabled by Fluorinated Surface and Compact Grain Stacking via Sulfuration of Ionic Liquid Coated Fluorides.

Metal-polysulfide batteries are attracting broad attention as conversion reaction systems of high theoretical energy density and low cost. However, their further applications are hindered by the low loading of active species, excess conductive additive, and loose (nanostructured) electrode networkss. Herein, we propose that compact grain stacking and surface fluorination are two crucial factors for achieving high-rate and long-life pyrite (FeS2) cathodes enabled by sulfurating ionic liquid wrapped open-framework fluorides. Both of the factors can accelerate the Li- and Na-driven transport across the pyrite-electrolyte interface and conversion propagation between adjacent grains. Such an electrode design enables a highly reversible capacity of 425 mAh/g after 1000 cycles at 1 C for Li storage and 450 mAh/g after 1200 cycles at 2 C for Na storage, even under a high loading of pyrite grains and ultrathin carbon coating (<2 nm). Its cathode energy density can reach to 800 and 350 Wh/kg for Li and Na cells, respectively, under a high power density of 10000 W/kg. The cross-linkage between ionic liquid and fluoride precursors appears to be a solution to the reinforcement of surface fluorination.

Bio-Inspired Surface Layer for the Cathode Material of High-Energy Density Sodium-Ion Batteries

P2-Cathode materials for sodium battery are usually active in the range of 2–4.3 V, but the decomposition of the electrolytic salt above 4 V versus Na+/Na is common. Arguably, the one of the concerns is the formation of HF after the reaction of the salts with water molecules, which are present as an impurity in the electrolyte. This HF ceaselessly attacks the active materials and gradually causes the failure of the electrode via electric isolation of the active materials. In this study, we report a bio-inspired b-NaCaPO4 nanolayer on a P2-type layered Na2/3[Ni1/3Mn2/3]O2 cathode material. The coating layers successfully scavenge HF and H2O, and excellent capacity retention was achieved with the b-NaCaPO4-coated Na2/3[Ni1/3 Mn2/3]O2 electrode. This retention was possible because a less acidic environment was produced in the Na cells during prolonged cycling. The intrinsic stability of the coating layer also assisted in delaying the exothermic decomposition reaction of the de-sodiated electrodes. We suggest formation and reaction mechanisms for the coating layers responsible for the excellent electrode performance. The suggested technology is promising for use with cathode materials in rechargeable sodium batteries to mitigate the effects of acidic conditions in Na cells. P2-type layered Na2/3[Ni1/3Mn2/3]O2 powders were synthesized by a conventional solid-state method. Na2CO3, Mn2O3, and NiO were thoroughly mixed. And then it was calcined at 1,000 °C for 12 h in air and then quenched, after which the pellet was immediately transferred into an Ar-filled glove box to minimize the adsorption of water and exposure to the CO2 in the air. Calcium nitrate and phosphoric acid were first dissolved in anhydrous ethanol at room temperature, and the as-synthesized active materials were added slowly to the solution. Then, the solution containing the active material was stirred continuously at 80 °C in a dry room, accompanied by the slow evaporation of the solvent. The as-prepared and bare Na2/3[Ni1/3Mn2/3]O2 powders were heated at 700 °C for 2 h in air. Also, the coated powders were characterized by XRD, SEM, and HR-TEM. Electrochemical properties of coated powders were examined by galvanostatic cycle test and electrochemical impedance spectroscopy. b-NaCaPO4 coatings shows uniform coating layers, as observed by TEM. Thickness of coating layer is of about 10nm. Electrochemical test with half cells in voltage range of 2.5 - 4.3 V at 25 oC indicates that coated materials have better capacity retention and coulombic efficiency, rate capability, and low resistance. Thin coating layers seem to effective to improve the electrochemical properties. Also, b-NaCaPO4 coatings give decrease of residual sodium and byproduct on the surface of particle, as confirmed by ToF-SIMS. Details will be mentioned at the conference site. Figure 1

Stabilizing a High-Energy-Density Rechargeable Sodium Battery with a Solid Electrolyte

Summary The cycling performance at 60°C of a Na 2 MnFe(CN) 6 /Na cell with a ceramic solid electrolyte is compared with that of a cell with an organic-liquid electrolyte operating at room temperature. Analysis of the electrode-electrolyte interfaces after charge-discharge cycling showed that a sodium-metal anode that wets the solid electrolyte can be plated and stripped reversibly dendrite free and that the dissolution of the cyano-perovskite Na 2 MnFe(CN) 6 cathode that occurs with an organic-liquid electrolyte is eliminated with the utilization of the solid electrolyte. This demonstration indicates that a high-energy-density and low-cost sodium rechargeable battery can be competitive for large-scale electric energy storage where both the anode and cathode problems are solved in an all-solid-state battery.

Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate

AbstractSurface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na2/3[Ni1/3Mn2/3]O2 is modified with ionic, conducting sodium phosphate (NaPO3) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH4H2PO4 with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na+/Na, the NaPO3‐coated Na2/3[Ni1/3Mn2/3]O2/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO3 nanolayers positively impact the cell performance by scavenging HF and H2O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO3 coating layer is delayed for decomposition to Mn3O4, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries.

Bioinspired Surface Layer for the Cathode Material of High‐Energy‐Density Sodium‐Ion Batteries

AbstractCathode materials are usually active in the range of 2–4.3 V, but the decomposition of the electrolytic salt above 4 V versus Na+/Na is common. Arguably, the greatest concern is the formation of HF after the reaction of the salts with water molecules, which are present as an impurity in the electrolyte. This HF ceaselessly attacks the active materials and gradually causes the failure of the electrode via electric isolation of the active materials. In this study, a bioinspired β‐NaCaPO4 nanolayer is reported on a P2‐type layered Na2/3[Ni1/3Mn2/3]O2 cathode material. The coating layers successfully scavenge HF and H2O, and excellent capacity retention is achieved with the β‐NaCaPO4‐coated Na2/3[Ni1/3Mn2/3]O2 electrode. This retention is possible because a less acidic environment is produced in the Na cells during prolonged cycling. The intrinsic stability of the coating layer also assists in delaying the exothermic decomposition reaction of the desodiated electrodes. Formation and reaction mechanisms are suggested for the coating layers responsible for the excellent electrode performance. The suggested technology is promising for use with cathode materials in rechargeable sodium batteries to mitigate the effects of acidic conditions in Na cells.

Thermoelectrochemical Activation of CoO in Na Cells

CoO is normally electrochemically inactive in sodium half-cells at room temperature. Here, it was found that CoO has significant electrochemical activity when cycled at 60°C (up to 550 mAh/g). In addition, CoO could be made electrochemically active at 30°C after undergoing one sodiation half-cycle at 60°C. Such in-situ thermoelectrochemical activation was found to be advantageous over ball milling. Combining ball milling with thermoelectrochemical activation, resulted in the highest reversible capacity achieved for CoO (300 mAh/g or 1800 Ah/L) and the best cycling retention.