RESUMEN

Co-free Ni-rich layered oxides are considered a promising cathode material for next-generation Li-ion batteries due to their cost-effectiveness and high capacity. However, they still suffer from the practical challenges of low discharge capacity and poor rate capability due to the hysteresis of Li-ion diffusion kinetics. Herein, based on the regulation of the lattice magnetic frustration, the Li/Ni intermixing defects as the primary origin of kinetic hysteresis are radically addressed via the doping of the nonmagnetic Si element. Meanwhile, by adopting gradient penetration doping, a robust Si-O surface structure with reversible lattice oxygen evolution and low lattice strain is constructed on Co-free Ni-rich cathodes to suppress the formation of surface dense  barrier layer. With the remarkably enhanced Li-ion diffusion kinetics in atomic and electrode particle scales, the as-obtained cathodes (LiNixMn1-xSi0.01O2, 0.6 ≤ x ≤ 0.9) achieve superior performance in discharge capacity, rate capability, and durability. This work highlights the coupling effect of magnetic structure and interfacial chemicals on Li-ion transport properties, and the concept will inspire more researchers to conduct an intensive study.

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Lithium hydride (LiH) has been widely recognized as the critical component of the solid-electrolyte interphase (SEI) in Li batteries. Although the formation mechanism and structural model of LiH in SEI have been extensively reported, the role in electro-performance of LiH in SEI is still ambiguous and has proven challenging to explored due to the complicated structure SEI and the lack of advanced in situ experimental technology. In this study, the isotopic exchange experiments combined with isotopic tracer experiments is applied to solidly illustrate the superior conductivity and Li+ conduction behavior of the LiH in natural SEI. Importantly, in situ transmission electron microscopy analysis is utilized to visualize the self-electrochemical decomposition of LiH, which is significantly distinctive from LiF and Li2O. The critical experimental evidence discovered by the work demonstrates ion transport behaviors of key components in the SEI, which is imperative for designing novel SEI and augurs a new area in optimizing the performance of lithium batteries.

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As a highly promising next-generation high-specific capacity anode, the industrial-scale utilization of micron silicon has been hindered by the issue of pulverization during cycling. Although numerous studies have demonstrated the effectiveness of regulating the inorganic components of the solid electrolyte interphase (SEI) in improving pulverization, the evolution of most key inorganic components in the SEI and their correlation with silicon failure mechanisms remain ambiguous. This study provides a clear and direct correlation between the lithium hydride (LiH) in the SEI and the degree of micron silicon pulverization in the battery system. The reverse lithiation behavior of LiH on micron silicon during de-lithiation exacerbates the localized stress in silicon particles and contributes to particle pulverization. This work successfully proposes a novel approach to decouple the SEI from electrochemical performance, which can be significant to decipher the evolution of critical SEI components at varied battery anode interfaces and analyze their corresponding failure mechanisms.

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A challenging task in solid oxide fuel cells (SOFCs) is seeking for an alternative electrolyte, enabling high ionic conduction at relatively low operating temperatures, i.e., 300-600 °C. Proton-conducting candidates, in particular, hold a significant promise due to their low transport activation energy to deliver protons. Here, a unique hierarchical TiO2-SrTiO3@TiO2 structure is developed inside an intercalated TiO2-SrTiO3 core as "yolk" decorating densely packed flake TiO2 as shell, creating plentiful nano-heterointerfaces with a continuous TiO2 and SrTiO3 "in-house" interfaces, as well the interfaces between TiO2-SrTiO3 yolk and TiO2 shell. It exhibits a reduced activation energy, down to 0.225 eV, and an unexpectedly high proton conductivity at low temperature, e.g., 0.084 S cm-1 at 550 °C, confirmed by experimentally H/D isotope method and proton-filtrating membrane measurement. Raman mapping technique identifies the presence of hydrogenated HO─Sr bonds, providing further evidence for proton conduction. And its interfacial conduction is comparatively analyzed with a directly-mixing TiO2-SrTiO3 composite electrolyte. Consequently, a single fuel cell based on the TiO2-SrTiO3@TiO2 heterogeneous electrolyte delivers a good peak power density of 799.7 mW cm-2 at 550 °C. These findings highlight a dexterous nano-heterointerface design strategy of highly proton-conductive electrolytes at reduced operating temperatures for SOFC technology.

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Metal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium-ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+-coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo-oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in-depth perception of failure mechanism and inspiration for realizing advanced conversion-type anode.

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Designing heterogeneous electrolytes with superior interface charge transfer is promising for low-temperature solid oxide fuel cells (LT-SOFCs). However, a rational construction with optimal interfaces to maximize ionic conduction remains a challenge. Here an in situ phase-transformation strategy is demonstrated to prepare a highly conductive heterogeneous electrolyte. A pristine LiNiO2-TiO2 nanocomposite precursor undergoes chemical reactions and phase-transformation upon heating and feeding H2, destroying the original phases, and forming new species, including an amorphous Li2CO3 scaffold within a (Ni, Co, Al, and Ti)-oxide (NCAT) matrix. It creates an intertwining and continuous network inside the electrolyte with plentiful interfaces. The in situ formed NCAT/Li2CO3 heterogeneous electrolyte displays superior ionic conductivity and impressive fuel cell performance. This work emphasizes the potential of rational heterogeneous structure design and interface engineering for LT-SOFC electrolyte through an in situ phase-transform approach. The generated interfaces enhance ion transport, presenting an opportunity for further optimizing electrolyte candidates, and lowering the operating temperatures of SOFCs.

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The application of lithium metal anode (LMA) is hindered by its poor cycle life which could be caused by lithium dendrite and critical volume change during cycling. Our group previously proposed an intermittent lithiophilic model for three-dimensional (3D) composite LMA, however, the lithium electrodeposition behavior was not discussed. To verify this model, this work proposed a facile design of a petaloid bimetallic metal-organic frameworks (MOFs) derived ZnCo2O4/ZnO (ZZCO) nanosheets modified carbon cloth (CC), i.e. CC@ZZCO, as a 3D host to achieve the intermittent deposition of lithium (Li). The material characterizations, density functional theory (DFT) calculations, lithium electrodeposition behaviors, and the electrochemical tests were investigated and the intermittent lithium deposition behavior was firstly confirmed. Thanks to the intermittent lithiophilic model, the composite LMA enabled a prolonged lifespan of 1500 h in a symmetrical cell under challenging conditions of 5 mA h cm-2 and 5 mA cm-2, and can maintain stable at 10C with an ultrahigh specific capacity of 110 mAh/g. Furthermore, it can also be coupled with a LiNi0.5Co0.2Mn0.3O2 (NCM523) and a high surface load of LiFePO4 (LFP) cathode (11.5 mg cm-2). This research might open a window for the understanding of the Li deposition behavior and pave the way to develop other alkali-metal-ion batteries.

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Low Na+ and electron diffusion kinetics severely restrain the rate capability of MoS2 as anode for sodium-ion batteries (SIBs). Slow phase transitions between 2H and 1T, and from NaxMoS2 to Mo and Na2S as well as the volume change during cycling, induce a poor cycling stability. Herein, an original Fe single atom doped MoS2 hollow multishelled structure (HoMS) is designed for the first time to address the above challenges. The Fe single atom in MoS2 promotes the electron transfer, companying with shortened charge diffusion path from unique HoMS, thereby achieving excellent rate capability. The strong adsorption with Na+ and self-catalysis of Fe single atom facilitates the reversible conversion between 2H and 1T, and from NaxMoS2 to Mo and Na2S. Moreover, the buffering effect of HoMS on volume change during cycling improves the cyclic stability. Consequently, the Fe single atom doped MoS2 quadruple-shelled sphere exhibits a high specific capacity of 213.3 mAh g-1 at an ultrahigh current density of 30 A g-1, which is superior to previously-reported results. Even at 5 A g-1, 259.4 mAh g-1 (83.68 %) was reserved after 500 cycles. Such elaborate catalytic site decorated HoMS is also promising to realize other "fast-charging" high-energy-density rechargeable batteries.

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Organic electrodes mainly consisting of C, O, H, and N are promising candidates for advanced batteries. However, the sluggish ionic and electronic conductivity limit the full play of their high theoretical capacities. Here, we integrate the idea of metal-support interaction in single-atom catalysts with π-d hybridization into the design of organic electrode materials for the applications of lithium (LIBs) and potassium-ion batteries (PIBs). Several types of transition metal single atoms (e.g., Co, Ni, Fe) with π-d hybridization are incorporated into the semiconducting covalent organic framework (COF) composite. Single atoms favorably modify the energy band structure and improve the electronic conductivity of COF. More importantly, the electronic interaction between single atoms and COF adjusts the binding affinity and modifies ion traffic between Li/K ions and the active organic units of COFs as evidenced by extensive in situ and ex situ characterizations and theoretical calculations. The corresponding LIB achieves a high reversible capacity of 1,023.0 mA h g-1 after 100 cycles at 100 mA g-1 and 501.1 mA h g-1 after 500 cycles at 1,000 mA g-1. The corresponding PIB delivers a high reversible capacity of 449.0 mA h g-1 at 100 mA g-1 after 150 cycles and stably cycled over 500 cycles at 1,000 mA g-1. This work provides a promising route to engineering organic electrodes.

RESUMEN

Rechargeable aprotic lithium (Li)-oxygen battery (LOB) is a potential next-generation energy storage technology because of its high theoretical specific energy. However, the role of redox mediator on the oxide electrochemistry remains unclear. This is partly due to the intrinsic complexity of the battery chemistry and the lack of in-depth studies of oxygen electrodes at the atomic level by reliable techniques. Herein, cryo-transmission electron microscopy (cryo-TEM) is used to study how the redox mediator LiI affects the oxygen electrochemistry in LOBs. It is revealed that with or without LiI in the electrolyte, the discharge products are plate-like LiOH or toroidal Li2O2, respectively. The I2 assists the decomposition of LiOH via the formation of LiIO3 in the charge process. In addition, a LiI protective layer is formed on the Li anode surface by the shuttle of I3 -, which inhibits the parasitic Li/electrolyte reaction and improves the cycle performance of the LOBs. The LOBs returned to 2e- oxygen reduction reaction (ORR) to produce Li2O2 after the LiI in the electrolyte is consumed. This work provides new insight on the role of redox mediator on the complex electrochemistry in LOBs which may aid the design LOBs for practical applications.

RESUMEN

Ni-rich layered oxide cathode materials demonstrate high energy densities for Li-ion batteries, but the electrochemically driven thermal runaway and mechanical degradation remain their long-standing challenges in practical applications. Herein, it presents a novel ZrV2 O7  (ZVO) coating with negative thermal expansion properties along the secondary particles and primary particle grain boundaries (GBs), to simultaneously enhance the structural and thermal stability of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811). It unveils that, such an architecture can significantly enhance the electronic conductivity, suppress the microcracks of GBs, alleviate the layered to spinel/rock-salt phase transformation, and meanwhile relieve the lattice oxygen loss by increasing the oxygen vacancy formation energy increased (1.43 vs 1.90 eV). Consequently, the ZVO-coated NCM811 material demonstrates a remarkable cyclability with 86.5% capacity retention after 100 cycles, and an outstanding rate performance of 30 C under a high-voltage of 4.6 V, outperforming the state-of-the-art literature. More importantly, the Li+ transportation can be readily blocked at 120 °C by the negative-thermal-expansion ZVO coating, thus avoiding the high-temperature thermal runaway.

RESUMEN

Li and Na metals with high energy density are promising in application in rechargeable batteries but suffer from degradation in the ambient atmosphere. The phenomenon that in terms of kinetics, Li is stable but Na is unstable in dry air has not been fully understood. Here, we use in situ environmental transmission electron microscopy combined with theoretical simulations and reveal that the different stabilities in dry air for Li and Na are reflected by the formation of compact Li2O layers on Li metal, while porous and rough Na2O/Na2O2 layers on Na metal are a consequence of the different thermodynamic and kinetics in O2. It is shown that a preformed carbonate layer can change the kinetics of Na toward an anticorrosive behavior. Our study provides a deeper understanding of the often-overlooked chemical reactions with environmental gases and enhances the electrochemical performance of Li and Na by controlling interfacial stability.

RESUMEN

Constructing all-solid-state lithium-sulfur batteries (ASSLSBs) cathodes with efficient charge transport and mechanical flexibility is challenging but critical for the practical applications of ASSLSBs. Herein, a multiscale structural engineering of sulfur/carbon composites is reported, where ultrasmall sulfur nanocrystals are homogeneously anchored on the two sides of graphene layers with strong SC bonds (denoted as S@EG) in chunky expanded graphite particles via vapor deposition method. After mixing with Li9.54 Si1.74 P1.44 S11.7 Cl0.3 (LSPSCL) solid electrolytes (SEs), the fabricated S@EG-LSPSCL cathode with interconnected "Bacon and cheese sandwich" feature can simultaneously enhance electrochemical reactivity, charge transport, and chemomechanical stability due to the synergistic atomic, nanoscopic and microscopic structural engineering. The assembled InLi/LSPSCL/S@EG-LSPSCL ASSLSBs demonstrate ultralong cycling stability over 2400 cycles with 100% capacity retention at 1 C, and a record-high areal capacity of 14.0 mAh cm-2 at a record-breaking sulfur loading of 8.9 mg cm-2 at room temperature as well as high capacities with capacity retentions of ≈100% after 600 cycles at 0 and 60 °C. Multiscale structural engineered sulfur/carbon cathode has great potential to enable high-performance ASSLSBs for energy storage applications.

RESUMEN

Cracks are ubiquitous in Ni-rich layered cathodes upon cycling in liquid electrolyte-lithium-ion batteries (LELIBs); however, their roles in the capacity decay are unclear. Furthermore, how cracks affect the performance of all solid-state batteries (ASSBs) has not been explored yet. Herein, cracks are created by mechanical compression in the pristine single crystal LiNi0.8Mn0.1Co0.1O2 (NMC811) and their roles in the capacity decay in solid-state batteries are asserted. These mechanically created fresh cracks are predominantly along the (003) planes with minor cracks along the planes slanted to the (003) planes, and both types of cracks contain little or no rock-salt phase, which is in sharp contrast to the chemomechanical cracks in NMC811 where rock-salt phase formation is ubiquitous. We reveal that mechanical cracks cause a significant initial capacity loss in ASSBs but little capacity decay during the subsequent cycling. In contrast, the capacity decay in LELIBs is principally governed by the rock salt phase and interfacial side reactions and thus does not result in an initial capacity loss, but a severe capacity decay during cycling.

RESUMEN

Sulfide electrolytes with high ionic conductivities are one of the most highly sought for all-solid-state lithium batteries (ASSLBs). However, the non-negligible electronic conductivities of sulfide electrolytes (≈10-8  S cm-1 ) lead to electron smooth transport through the sulfide electrolyte pellets, resulting in Li dendrite directly depositing at the grain boundaries (GBs) and serious self-discharge. Here, a grain-boundary electronic insulation (GBEI) strategy is proposed to block electron transport across the GBs, enabling Li-Li symmetric cells with 30 times longer cycling life and Li-LiCoO2 full cells with three times lower self-discharging rate than pristine sulfide electrolytes. The Li-LiCoO2 ASSLBs deliver high capacity retention of 80 % at 650 cycles and stable cycling performance for over 2600 cycles at 0.5 mA cm-2 . The innovation of the GBEI strategy provides a new direction to pursue high-performance ASSLBs via tailoring the electronic conductivity.

RESUMEN

Currently, one of the main reasons for the ineffectiveness of tumor treatment is that the abnormally high tumor interstitial pressure (TIP) hinders the delivery of drugs to the tumor center and promotes intratumoral cell survival and metastasis. Herein, we designed a "nanomotor" by in situ growth of Ag2S nanoparticles on the surface of ultrathin WS2 to fabricate Z-scheme photocatalytic drug AWS@M, which could rapidly enter tumors by splitting water in interstitial liquid to reduce TIP, along with O2 generation. Moreover, the O2 would be further converted to reactive oxygen species (ROS), accompanied by increased local temperature of tumors, and the combination of ROS with thermotherapy could eliminate the deep tumor cells. Therefore, the "nanomotor'' could effectively reduce the TIP levels of cervical cancer and pancreatic cancer (degradation rates of 40.2% and 36.1%, respectively) under 660 nm laser irradiation, further enhance intratumor drug delivery, and inhibit tumor growth (inhibition ratio 95.83% and 87.61%, respectively), and the related mechanism in vivo was explored. This work achieves efficiently photocatalytic water-splitting in tumor interstitial fluid to reduce TIP by the nanomotor, which addresses the bottleneck problem of blocking of intratumor drug delivery, and provides a general strategy for effectively inhibiting tumor growth.

Asunto(s)

RESUMEN

Sex Sy is considered as a promising cathode material as it can deliver higher energy density than selenium (Se) and offer improved conductivity and enhanced reaction kinetics compared with S. However, the electrochemistry of the Li-SeS2 all-solid-state battery (ASSB) has not been well understood to date. Herein the electrochemistry of Li-SeS2 battery was revealed by in-situ transmission electron microscopy. The charge products were phase-separated Se and S, rather than the widely believed SeS2 . Among the various Sex Sy cathodes, SeS2 achieved the best electrochemical performance. The Li-SeS2 ASSB delivered a high reversible capacity of 1052 mAh g-1 at 1 A g-1 over 350 cycles, and a high areal capacity of 4 mAh cm-2 was also achieved with a high cathode mass loading of 7.6 mg cm-2 . These results represent the best performance achieved to date in the Li-SeS2 ASSB and brings us one step closer toward its practical applications.

RESUMEN

The absence of lymphatic vessels in tumors leads to the retention of interstitial fluid, and the formation of an inverse pressure difference between the tumor and blood vessels hinders drug delivery deep into the tumor, which leads to tumor recurrence and metastasis. Therefore, we designed a novel strategy to downregulate tumor interstitial fluid pressure (TIFP) by water splitting in the tumor interstitium based on piezoelectric catalysis nanomedicine. First, the chemotherapeutic drug doxorubicin (DOX) was loaded on the piezoelectric catalytic material MoS2 and then encapsulated with tumor cell membrane (CM) to obtain MD@C. MD@C could not only target the tumor through homologous targeting but, more importantly, also triggered piezoelectric catalytic water splitting under ultrasound (US) stimulation; as a result, the TIFPs of U14 and PAN02 tumor-bearing mice were reduced to 57.14% and 45.5%, respectively, and the tumor inhibition rates of MD@C were 96.75% and 99.21%, which increased the perfusion of blood-derived drugs in the tumors. Moreover, the hydroxyl radicals generated by piezoelectric catalysis could effectively inhibit the growth of tumors in combination with DOX. Consequently, the piezoelectric catalytic water splitting strategy of MD@C can enhance drug delivery, providing a new universal platform for the treatment of solid malignant tumors.

Asunto(s)

RESUMEN

Selenium (Se), whose electronic conductivity is nearly 25 orders higher than that of sulfur (S) and whose theoretical volumetric capacity is 3254 mAh cm-3, is considered as a potential alternative to S to overcome the poor electronic conductivity issue of the S cathode in the lithium (Li)-S battery. However, the study of the Li-Se battery, particularly a Li-Se all-solid-state battery (ASSB), is still in its infancy. Herein, we report the performance of Li-Se ASSBs at both room temperature (RT) and high temperature (HT, 50 °C), using a Li10Si0.3PS6.9Cl1.8 (LSPSCl) solid-state electrolyte and Li-In anode. With a Se loading of 7.6 mg cm-2, the Li-Se battery displayed a record high reversible capacity of 6.8 mAh cm-2 after 50 cycles at HT, which exceeds the theoretical areal capacity of 5.2 mAh cm-2 for Se. Moreover, the RT Li-Se ASSB delivered an initial areal capacity of about 2 mAh cm-2 at a current density of 1 A g-1 for 1200 cycles with a capacity retention of 67%. Cryo-electron microscopy revealed that the excessive capacity of Se at HT can be attributed to the formation of a previously unknown S5Se4 phase during charging, which participated reversibly in a subsequent redox reaction. The formation of the S5Se4 phase originated from the reaction of Se with S, which was generated by the decomposition of LSPSCl at HT. These results unlock the electrochemistry of a Li-Se ASSB, suggesting that a Li-Se ASSB is a viable alternative to a Li-S battery for energy storage applications.

RESUMEN

Conversion-type cathodes such as metal fluorides, especially FeF2 and FeF3 , are potential candidates to replace intercalation cathodes for the next generation of lithium ion batteries. However, the application of iron fluorides is impeded by their poor electronic conductivity, iron/fluorine dissolution, and unstable cathode electrolyte interfaces (CEIs). A facile route to fabricate a mechanical strong electrode with hierarchical electron pathways for FeF2 nanoparticles is reported here. The FeF2 /Li cell demonstrates remarkable cycle performances with a capacity of 300 mAh g-1 after a record long 4500 cycles at 1C. Meanwhile, a record stable high area capacity of over 6 mAh cm-2 is achieved. Furthermore, ultra-high rate capabilities at 20C and 6C for electrodes with low and high mass loading, respectively, are attained. Advanced electron microscopy reveals the formation of stable CEIs. The results demonstrate that the construction of viable electronic connections and favorable CEIs are the key to boost the electrochemical performances of FeF2 cathode.