Cation Migration Research Articles

Ion Migration-Induced Degradation and Efficiency Roll-off in Quasi-2D Perovskite Light-Emitting Diodes.

Quasi-2D perovskites have attracted wide attention as the emitter of light-emitting diodes (LEDs) in recent years because of the ease of obtaining high external quantum efficiencies (EQEs). However, the quick degradation under continuous operation and significant EQE roll-off at high current densities are issues that need to be overcome for future practical applications using quasi-2D perovskite LEDs (PeLEDs). In this context, we discuss the mechanism of the degradation and EQE roll-off on the basis of ion migration. The migration of ligand cations though domain boundaries of quasi-2D perovskite films induces the gradual loss of defect passivation at the boundaries, which results in the reversible PeLED degradation and severe EQE roll-off. When the device operation time is long, the mobile cations enter and interact with the electron transport layer, leading to the stage of irreversible PeLED degradation. The device degradation mechanisms we discovered here are constructive for developing quasi-2D PeLEDs with better operational durability.

Sequential delithiation behavior and structural rearrangement of a nanoscale composite-structured Li1.2Ni0.2Mn0.6O2 during charge\u2013discharge cycles

Lithium- and manganese-rich layered oxides (LMRs) are promising positive electrode materials for next-generation rechargeable lithium-ion batteries. Herein, the structural evolution of Li1.2Ni0.2Mn0.6O2 during the initial charge–discharge cycle was examined using synchrotron-radiation X-ray diffraction, X-ray absorption spectroscopy, and nuclear magnetic resonance spectroscopy to elucidate the unique delithiation behavior. The pristine material contained a composite layered structure composed of Ni-free and Ni-doped Li2MnO3 and LiMO2 (M = Ni, Mn) nanoscale domains, and Li ions were sequentially and inhomogeneously extracted from the composite structure. Delithiation from the LiMO2 domain was observed in the potential slope region associated with the Ni2+/Ni4+ redox couple. Li ions were then extracted from the Li2MnO3 domain during the potential plateau and remained mostly in the Ni-doped Li2MnO3 domain at 4.8 V. In addition, structural transformation into a spinel-like phase was partly observed, which is associated with oxygen loss and cation migration within the Li2MnO3 domain. During Li intercalation, cation remigration and mixing resulted in a domainless layered structure with a chemical composition similar to that of LiNi0.25Mn0.75O2. After the structural activation, the Li ions were reversibly extracted from the newly formed domainless structure.

Ni–Li anti-site defect induced intragranular cracking in Ni-rich layer-structured cathode

High packing density of Ni-rich lithium transition metal oxide (LTMO) cathodes contribute to high energy density of lithium-ion batteries, however, resulting in severe intergranular and intragranular cracking issues. Most of previous works are focused on understanding the behaviors of intergranular cracks. However, the incubation mechanism of intragranular crack, especially at atomic scale, is still unclear though they are one of the main obstacles for practical application of Ni-rich LTMO cathode. Here, we reveal at atomic scale the intragranular cracking mechanism of LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode during cycling processes. Ni–Li anti-site defect enrichment region with lattice distortion has been identified as the nucleation site for intragranular crack in the primary particle. The growth of intragranular crack can be ascribed to the strain difference between layered phase and electrochemical inactive phase and the Columbic repulsion in cation-rich area, which originate from the Ni–Li anti-site defect in transformed structure. The golden strategy to acquire stable high-energy cathode lies in suppressing the migration of cations before cracks occur, providing new insights for the design of high-performance Ni-rich LTMO cathodes. We reveal at atomic scale the intragranular cracking mechanism of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode during cycling processes. At atomic-scale, nucleation at Ni-Li anti-site defect enrichment region with lattice distortion has been firstly identified as the startup mechanism for intragranular crack in NMC811 cathode. The strain difference between layered phase and electrochemical inactive phase and the Columbic repulsion in the cation-rich area are considered as the two driving forces for the development of intragranular crack. Both of them originate from Ni-Li anti-site defect in transformed structure. • Ni-Li anti-site defect enrichment region has been identified as nucleation site for intragranular crack of NMC811. • The strain difference and the Columbic repulsion are considered as two driving forces for the growth of intragranular crack. • Suppress the migration of cations is a golden strategy to acquire high energy cathode with long cycle life.

Cluster-Type Filaments Induced by Doping in Low-Operation-Current Conductive Bridge Random Access Memory.

Conductive bridge random access memory (CBRAM) is one of the most representative emerging nonvolatile memories in virtue of its excellent performance on speed, high-density integration, and power efficiency. Resistive switching behaviors in CBRAM involving the formation/rupture of metallic conductive filaments are dominated by cation migration and redox processes. It is all in the pursuit to decrease the operation current for low-power consumption and to enhance the current compliance-dependent reliability. Here, we propose a novel structure of Pt/TaOx:Ag/TaOx/Pt with nonvolatile switching at ∼1 μA and achieve a five-resistance-state multilevel cell operation under different compliance currents. Different from the nanocone-shaped filaments reported in traditional Ag top electrode devices, cluster-type filaments were captured in our memory devices, explaining the low-operation current-resistive switching behaviors. Meanwhile, Cu-doped counterpart devices also display similar operations. Such memory devices are more inclined to achieve low-power consumption and offer feasibility to large-scale memory crossbar integration.

Microstructural understanding of the oxidation of an austenitic stainless steel in high-temperature steam through advanced characterization

It is well-known that steels always oxidize faster in the environments containing water vapour than in dry oxygen. Due to the difficulties in obtaining necessary experimental scale of observations, the mechanisms responsible for the steam-accelerated oxidation are still unclear. Through a combination of multiscale characterization techniques, the surface oxide film formed on an Fe-17Cr-9Ni stainless steel after exposure to high-temperature steam has been studied in detail. The characterization results obtained in this study reveal that the inner oxide layer actually consists of two phases Fe-Ni austenite and FeCr2O4 oxide, which formed due to internal oxidation. The classic internal oxidation model underestimates the thickness of the inner oxide layer by one order of magnitude. This difference can be explained by the existence of fast diffusion channels in the inner oxide layer. This study provides direct evidence of a high density of nanopores in the oxide phase of the internal oxide layer, which can act as fast-diffusion channels if interconnected, and proposes their mechanisms of formation, a consequence of water dissociation-induced protons promoting the formation, migration, and clustering of both cation and anion vacancies.

Sr2Nb3O10 nanosheet thin film grown via LB method for high-performance planar-type pseudocapacitor

The electrochemical properties of a two-dimensional metal-oxide Sr2Nb3O10 (SNO) nanosheet thin film were investigated for application to pseudocapacitors. Smooth migration of cations was expected to occur in the SNO thin film because of a large gap between the SNO nanosheets along the [0 0 1] direction. A thin film with 10 SNO nanosheets was well deposited on a Pt/Ti/SiO2/Si substrate using the Langmuir–Blodgett method, and it exhibited a large (0 0 1) interplanar distance of 1.83 nm owing to the presence of TBA+ ions. The TBA+ ions were removed from the SNO thin-film electrode after the second charge/discharge cycle in the LiCl electrolyte with a slight decrease in the (0 0 1) interplanar distance (1.65 nm). The Li+ ions were intercalated and deintercalated during the charge/discharge cycle, resulting in good capacitive behavior. The planar-type SNO pseudocapacitor exhibited rectangular cyclic-voltammetry curves and triangular charge/discharge curves. Moreover, capacity retention was 85% after 5000 cycles, indicating that the pseudocapacitor had ideal capacitive behavior with excellent cycling stability. The developed SNO pseudocapacitor exhibited a higher power density (0.2 W/cm3) and energy density (4.9 × 10-3 W h/cm3) than previously reported thin-film capacitors. Therefore, the SNO thin film is a good candidate material for pseudocapacitors.

Microstructures of a SiC–ZrC Ceramic Fiber Derived from a Polymeric Precursor

Continuous ceramic fiber comprising silicon carbide–zirconium carbide (SiC–ZrC) binary phases was obtained through melt spinning, electron-beam curing and pyrolysis of a pre-ceramic precursor of polyzirconocenecarbosilanes (PZCS). After pyrolysis and heat treatment, ZrC particles with mean diameters of 15–20 nm were formed and homogeneously dispersed in a matrix of fine crystalline β-SiC with an average grain size of 6–10 nm. Concentration of Zr in the fiber varies from 14.88% to 17.45% by mass. Fibers consisting of near-stoichiometric ZrC and SiC with little free carbon can be obtained through pyrolysis decarbonization of the as-cured fiber in hydrogen from room temperature to 1000 °C, and subsequently heat treatment in argon up to 1600 °C for 1 h. High-temperature treatment of these amorphous inorganic fibers leads to crystallization of the binary phases of β-SiC and ZrC. The removal of free carbon under hydrogen results in more rapid growth of β-SiC and ZrC crystals, in which obvious aggregation of the dispersed ZrC particles among the continuous β-SiC matrix can be ascribed to a fast migration of Zr cation.

(Invited) Understanding Anion and Cation Migration in Hybrid Perovskite Solar Cells

Hybrid perovskites are popular materials for realizing low cost, third generation solar cells. Certified power conversion efficiencies of laboratory scale devices now exceed 20%. Despite engineering advances, which have led to these advances, hybrid perovskites are still plagued by instabilities. The best known relate to moisture instabilities. Less, however, is understood about intrinsic limitations of these materials, stemming from both anion and cation migration under illumination or under bias. Understanding the microscopic origin of these instabilities as well as suppressing them represents one of the last major open scientific questions, preventing their commercialization. In this talk, I therefore summarize what is known about anion and cation migration and discuss results from microscopic, spatially-resolved optical measurements we have conducted on both thin films and solar cells.

Correlation between Cation Disordering and the Anionic Redox Chemistry in Li-Rich Layered Oxides

To satisfy our increasing dependence on the high energy storage electronics, Li-rich layered oxides (Li[LixM1-x]O2, M = Ni, Co, Mn, Ru, Ir, etc) have attracted significant attention as cathode materials for lithium-ion batteries in recent years. This class of cathode materials exhibit promising capacities, up to 300 mAh/g, due to accumulative transition metal and oxygen redox reaction1–5. Additional capacity in this class of Li-rich cathode material is attributed to the anionic redox which is irreversible or partially reversible oxygen evolution6,7 and reversible O2-/n- redox1,3,4,8. Luo el at.1 demonstrated that the localized electron holes on oxygen coordinated by Mn4+ and Li+ ions is promoted by the relatively more ionic interactions of O-(Mn/Li) than O-(Ni/Co) interactions at the result of the oxygen oxidation. In our previous study2, at least partially reversible oxygen evolution was observed in 0.4Li2MnO3-0.6LiMn0.5Ni0.5O2 by using Reitveld refinement of high resolution powder diffraction patterns. In the case of 4d (Ru) and 5d (Ir) transition metal-based Li-rich cathode materials, reversible anionic redox was confirmed by X-ray photoelectron spectroscopy (XPS)3,4. Even though the participation of oxygen in redox activity in Li2MnO3 results in partial oxygen evolution with irreversible structural changes9, oxygen redox reaction is stabilized by the reversible peroxo-dimers (O2 n-) formation in the Li2MO3-based (M = Ru, Ir) Li-rich cathode materials due to the high covalent metal-oxygen environment in Ru- and Ir-based lithium-rich cathode materials. However, Seo et al.10 identified the structural and chemical origin of the anionic redox activity which preferentially takes place along the Li-O-Li configurations (non-bonding O 2p states) in Li-rich layered oxides and cation-disordered oxides by using ab initio calculations based on DFT. The electrons in Li-O-Li states are higher energy than those in the other O 2p states owing to their unhybridized O 2p and Li 2s orbitals without taking into account the covalency between the transition metal and oxygen. Through the significant research efforts, anionic redox mechanism seems to be well established. In the case of Na2RuO3, extra anionic capacity is enabled in honeycomb-ordered Na2RuO3 due to the ordered intermediate Na1RuO3 phase which can accommodate the frontier orbital reorganization11, meanwhile, transition metal migration into the empty Li sites is closely associated with the anionic redox as a result of the structural disordering in Li1.17Ni0.21Co0.08Mn0.54O2 5 and Li2IrxSn1-xO3 systems12. It is still under debating whether such manifold anionic chemistry will be solved in terms of transition metals (3d, 4d, and 5d) or alkali metals (Li and Na) or bulk and local structure. In addition, the different reaction mechanism is confirmed between multivalent iridium redox (Ir4+/5.5+)12 and cumulative iridium (Ir4+/5+) and oxygen (O2-/n-) redox13 even in the same C2/m space group of Li2IrO3 materials.Herein, redox mechanism of Li2IrO3 was investigated as a model compound for Li-rich cathode material to understand the key structural differences that lead to anionic redox activity through the synchrotron-based analysis. The local environment, not the composition itself in Li-rich materials, is one of the major factors affecting the redox reaction. We demonstrate that the in-plane disordering in the transition metal layer play a critical role in cation migration and anionic redox, and that cation migration also can trigger the anionic redox reactions. These fundamental insights about Li-rich material family are critical for further development of anionic redox-based cathode materials. In-plane ordering in pristine state with the same composition of Li2IrO3 has a major impact on cation migration and reversible anion redox. Based on the experimental data, detailed findings and discussion will be presented in the 237th ECS meeting.

Electrolyte, Solvation Shell and Interphase for Ca and Mg Metal Anode Based Batteries

Various metals have been used as battery anodes in electrochemical cells ever since the birth of the batteries with Volta’s pile and in the first commercialized primary (Zn/MnO2, Leclanché 1866) and secondary (Pb/acid, Planté 1859) batteries. Li-MoS2 cells, employing Li metal anodes, with specific energies two to three times higher than both Ni/Cd and Pb/acid cells, were withdrawn from the market due to safety issues related to dendrites growth. Instead, electrodeposition of Mg and Ca appears to be less prone to dendrite formation.[1,2] Pioneering work by Aurbach et al. in the early 1990’s showed a surface-film controlled electrochemical behavior of Ca and Mg metal anodes in electrolytes with conventional organic solvents.[3,4] The lack of metal plating was attributed to the poor divalent cation migration through the passivation layer.Nevertheless, recent demonstration of Ca and Mg plating and stripping in the presence of a passivation layer or an artificial interphase [2,5,6] has paved the way for assessment of new electrolyte formulations with high resilience towards oxidation. However, several challenges remain to be tackled for the development of Ca and Mg based batteries.[7,8] Among these, the need for reliable electrochemical test protocols, mass transport limitations and high desolvation energies (due to strong cation-solvent and cation–anion interactions) are implied.[9, 10] Here, the reliability of electrochemical set-ups involving multivalent chemistries is discussed, and a systematic investigation on the impact of the electrolyte formulation on the cation solvation structure and transport is presented.

Microscopic Mechanism of Carbon-Dopant Manipulating Device Performance in CGeSbTe-Based Phase Change Random Access Memory.

Carbon (C)-doped Ge2Sb2Te5 material is a potential candidate in phase change random access memory (PCRAM) because of its superb thermal stability and ultrahigh cycle endurance. Unfortunately, the role and distribution evolution of C-dopant is still not fully understood, especially in practical industrial devices. In this report, with the aid of advanced spherical aberration corrected transmission electron microscopy, the mechanism of microstructure evolution manipulated by C-dopant is clearly defined. The grain-inner C atoms distinctly increase cationic migration energy barriers, which is the fundamental reason for promoting the thermal stability of metastable face-centered-cubic phase and postponing its transition to the hexagonal structure. By current pulses stimulation, the stochastic grain-outer C clusters tend to aggregate in the active area by breaking C-Ge bonding; thus, grain growth and elemental segregation are effectively suppressed to improve device reliability, for example, lower SET resistance, shorter SET time, and enlarged RESET/SET ratio. In short, the visual distribution variations of C-dopant can manipulate the performance of the PCRAM device, having much broader implications for optimizing its microstructure transition and understanding C-doped material system.

A Superlattice-Stabilized Layered Oxide Cathode for Sodium-Ion Batteries.

Sodium-ion batteries are in high demand for large-scale energy storage applications. Although it is the most prevalent cathode, layered oxide is associated with significant undesirable characteristics, such as multiple plateaus in the charge-discharge profiles, and cation migration during repeated cycling of Na-ions insertion and extraction, which results in sluggish kinetics, capacity loss, and structural deterioration. Here, a new strategy, i.e., the manipulation of transition-metal ordering in layered oxides, is proposed to show a prolonged charge-discharge plateau and cation-migration-free structural evolution. The results demonstrate that the transition-metal ordering with a honeycomb-type superlattice can adjust the crystal lattice and suppress cation migration by modifying the crystal strain to realize a large reversible capacity and excellent cycling performance, which are not characteristics of the widely used common layered oxides. These findings can provide new insight that can be used to improve the design of high-performance electrode materials for secondary-ion batteries.

Tracking the Influence of Thermal Expansion and Oxygen Vacancies on the Thermal Stability of Ni-Rich Layered Cathode Materials.

The ever‐growing demand for high‐energy lithium‐ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium‐ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni‐rich cathode materials based on a systematic synchrotron‐based X‐ray study of Li0.33Ni0.5+ xCo0.2Mn0.3‐ xO2 (x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered‐to‐spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.

High-Voltage Cycling Induced Thermal Vulnerability in LiCoO2 Cathode: Cation Loss and Oxygen Release Driven by Oxygen Vacancy Migration.

The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally attributed to the phase transitions from the layered structure to spinel and rocksalt structures that contain less lattice oxygen. Here, a different degradation pathway in LiCoO2 is found, through oxygen vacancy facilitated cation migration and reduction. This process leaves undercoordinated oxygen that gives rise to oxygen release while the structure integrity of the defect-free region is mostly preserved. This oxygen release mechanism can be called surface degradation due to the kinetic control of the cation migration but has a slow surface to bulk propagation with continuous loss of the surface cation ions. It is also strongly correlated with the high-voltage cycling defects that end up with a significant local oxygen release at low temperatures. This work unveils the thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach.

Gold Redox Catalysis with a Selenium Cation as a Mild Oxidant.

Gold-catalyzed alkyne and allene diselenations were developed. Excellent regioselectivity (trans) and good to excellent yields were achieved (up to 98 % with 2 % catalyst loading) with a wide range of substrates. Mechanistic investigation revealed the formation of a vinyl gold(I) intermediate followed by an intermolecular selenium cation migration, suggesting that a gold(I/III) redox process was successfully implemented under mild conditions.

Development of a new family of spinel nano-ceramic ferrites based on Ni1-xHoxFe2O4 (0 ≤ x ≤ 0.07) via a 1,4-dithioerythritol assisted polyol technique

A new family of nanoferrites composed of Ni1-xHoxFe2O4 (0 ≤ x ≤ 0.07) was developed via a 1,4-dithioerythritol assisted polyol technique. The influence of holmium (Ho) cations on the lattice constant, nanoparticle size, and stoichiometry of the cubic spinel structures were examined using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). Doping with Ho cations (up to 3 wt%) in Ni1-xHoxFe2O4 causes an increase of the nanocrystal diameter and the lattice constant. The FTIR and Raman measurements showed the migration of iron cations from tetrahedral to octahedral sublattices due to incorporation of Ho cations. Magnetic (M-H) measurements demonstrated that Ni0.97Ho0.03Fe2O4 exhibits a remarkable improvement of the coercive field (129.7 Gauss) and the saturation magnetization (36.6 emu/g) compared with NiFe2O4, for which the coercive field is 23.3 Gauss and the saturation magnetization is 7.5 emu/g. The enhancement of magnetic constants by more than five orders of magnitude for Ni1-xHoxFe2O4 nano-ceramics make them promising as magnetic catalytic materials and magnetic nanocarriers for drug delivery applications.

A quantum mechanical study on the application of inorganic BC2N nanotubes in the Na-ion batteries

We scrutinized the potential application of a BC2N nanotube as an anode material for the Na-ion batteries (NIBs) using B3LYP-gCP-D3/6-31G* model chemistry. Two kinds of hexagonal rings (B2C2N2 (α) and BC4N (β)) are identified, being nonaromatic based on the NMR calculations. The Na cation adsorbs on the α and β rings with adsorption energies of −46.7 and −38.1 kcal/mol via different mechanisms, namely, cation-lone-pair and cation-π interactions, respectively. The predicted adsorption energy for Na atom is −12.0 kcal/mol, including a large dispersion term of −5.7 kcal/mol. The BC2N nanotube preserves its initial structure during the Na/Na+ adsorption because of a small calculated deformation energy. The maximum energy barrier for an Na cation migration on the tube surface is 13.7 kcal/mol which yields a diffusion coefficient of 3.70 × 10−10 cm2/s. Thus, the BC2N nanotube provides a great ion mobility leading to a faster charge/discharge rate. The predicted cell voltage for BC2N nanotube is 1.58 V, being larger than that of different BN and AlN nanostructures and graphene. All of above offer the BC2N nanotube as a plausible anode material for application in the NIBs.

Boosting Sodium Storage in Two-Dimensional Phosphorene/Ti3C2Tx MXene Nanoarchitectures with Stable Fluorinated Interphase.

The stacking of complementary two-dimensional (2D) materials into hybrid architectures is desirable for batteries with enhanced capacity, fast charging, and long lifetime. However, the 2D heterostructures for energy storage are still underdeveloped, and some associated problems like low Coulombic efficiencies need to be tackled. Herein, we reported a phosphorene/MXene hybrid anode with an in situ formed fluorinated interphase for stable and fast sodium storage. The combination of phosphorene nanosheets with Ti3C2Tx MXene not only facilitates the migration of both electrons and sodium cations but also alleviates structural expansion of phosphorene and thereby improves the cycling performance of the hybrid anode. X-ray photoelectron spectroscopy in-depth analysis reveals that the fluorine terminated MXene stabilize the solid electrolyte interphase by forming fluorine-rich compounds on the anode surface. Density functional theory calculations confirm that the sodium affinities and diffusion kinetics are significantly enhanced in the phosphorene/MXene heterostructure, particularly in the phosphorene/Ti3C2F2. As a result, the hybrid electrode achieved a high reversible capacity of 535 mAh g-1 at 0.1 A g-1 and superior cycling performance (343 mAh g-1 after 1000 cycles at 1 A g-1 with a capacity retention of 87%) in a fluorine-free carbonate electrolyte.

Superionic conduction in low-dimensional-networked anti-perovskites

Fast cationic conduction is necessary for a number of solid-state technologies and is particularly critical for solid-state batteries as solid electrolytes are typically poor conductors. This article illustrates the concept of low-dimensional networked (low-DN) anti-perovskite via first-principles computations and shows that superionicity (i.e. the conductivity is above 1 ​mS ​cm−1 at room temperature) can be achieved by lowering the dimensionality of the connected octahedra of the anti-perovskite. In particular, we use the Li–O–Cl model system and study the diffusion of Li in 3DN-Li3OCl, 2DN-Li4OCl2, 1DN-Li5OCl3, and 0DN-Li6OCl4. We find that the lower the dimensionality, the lower the Li migration barriers and the higher the diffusion coefficients are. We attribute this improved ionic conduction to the decreased size of the bottlenecks and the softening of the rotation modes of the octahedra in the structure. To further explore the concept of low-DN anti-perovskites, we screen 256 model materials in the I-VI-VII group chemical space by computing the phase stability and bandgap of 3DN-X3BA, 2DN-X4BA2, 1DN-X5BA3, and 0DN-X6BA4 (X ​= ​Li, Na, K, Rb; B ​= ​O, S, Se, Te; and A ​= ​F, Cl, Br, I). The calculations suggest that 20% of the structures might be synthesized and a number of them possess reasonable cationic migration barriers (<400 ​meV). This study puts forward a new principle for designing solid superionic conductors by lowering the dimensionality of the primitive structural units.

Tuning cation migration

Through engineering of oxygen stacking and cation–cation interactions, a methodology to design high-energy and long-cycle-life lithium-rich battery materials is proposed.