Electrode Engineering by Atomic Layer Deposition for Sodium‐Ion Batteries: From Traditional to Advanced Batteries

Sodium‐ion batteries (SIBs) have emerged as one of the most promising and competitive energy storage systems due to abundant sodium resources and its environmentally friendly features. However, further improvements in the engineering of the SIB electrode/electrolyte interphase—which directly determines the Na‐ion transfer behavior, material structure stability, and sodiation/desodiation property—are highly recommended to meet the continuously increasing requirements for secondary power sources. Reasonably speaking, to promote SIBs, the advanced and controllable interphase/electrode engineering approach exhibits promise by rationally designing the bulk electrode and generating a well‐defined interphase. Atomic layer deposition (ALD) technology, with atomic‐scale deposition, superior uniformity, excellent conformality, and a self‐limiting nature, is thus expected to address the current challenges facing SIBs in terms of low energy density, limited cycling life, and structural instability, and to promote innovations such as multifunctional electrodes and nanostructured materials for advanced SIBs. This review summarizes and discusses the most recent advancements in the interphase engineering of SIBs by ALD via modifying traditional electrodes and designing advanced electrodes (such as 3D, organic, and protected sodium metal electrodes). Furthermore, based on the recent critical progress and current scientific understanding, future perspectives for the engineering of next‐generation SIB electrodes by ALD can be provided.     

High Tap Density Co and Ni Containing P2‐Na0.66MnO2 Buckyballs: A Promising High Voltage Cathode for Stable Sodium‐Ion Batteries

Constructing high voltage (>4.5 V) cathode materials for sodium‐ion batteries has emerged in recent years to replace lithium batteries for large scale energy storage applications. Herein, an electrochemically stable Na_0.66(Ni_0.13Mn_0.54Co_0.13)O₂ (Na‐NMC) buckyballs with an uniform size of 5 µm and a high tap density of 2.34 g cm^?3, which exhibit excellent cyclability even at the high current with a cut‐off voltage of 4.7 V, is demonstrated. The Na‐NMC buckyballs are prepared from (Ni_0.13Mn_0.54Co_0.13)CO₃ (NMC) precursor synthesized using a facile hydrothermal method. The Na‐NMC delivers a reversible capacity of around 120 mAh g^?1 between 4.7 and 2 V at 1 C rate along with an excellent cyclic stability (90%) until 150 cycles, which is one of the best outcomes among the reported P2‐type cathodes tested at the high operating voltage range. Furthermore, Na‐NMC‐180 buckyballs with a high tap density is offering an enhanced volumetric energy density, a superior rate performance and an outstanding cyclic stability. The X‐ray adsorption fine structure analysis is used to study the local electronic structure changes around the Co, Mn, and Ni after cycling process at 1 C rate. The findings open opportunities for tailoring high‐performance and high‐energy cathode materials for sodium‐ion batteries.     

Constructing Safe and Durable High‐Voltage P2 Layered Cathodes for Sodium Ion Batteries Enabled by Molecular Layer Deposition of Alucone

Sodium ion batteries are a promising next‐generation energy storage device for large‐scale applications. However, the high voltage P2–O2 phase transition (>4.25 V vs Na/Na⁺) and metal dissolution of P2 layered cathodes into the electrolyte result in severe capacity fading, which is a major setback to fabricate high energy devices. Hence, it is essential to design an appropriate strategy to enhance interfacial behaviors to obtain safe and stable high voltage sodium ion batteries. Herein, an ultrathin alucone layer deposited through molecular layer deposition (MLD) is employed to stabilize the structure of a P2‐type layered cathode cycled at a high cut‐off voltage (>4.45 V) for the first time. The alucone coated P2‐type Na_0.66Mn_0.9Mg_0.1O₂ (NMM) cathode exhibits an 86% capacity retention after 100 cycles between 2 and 4.5 V at 1 C, demonstrating substantial improvement compared to pristine (65%) and Al₂O₃‐coated (71%) NMM cathodes. Furthermore, the mechanically robust and conductive nature of the organometallic thin film enhances the rate capability relative to the pristine NMM electrode. This work reveals that the MLD of alucone on cathodes is a promising approach to improve the cycle stability of sodium ion batteries at high cut‐off voltages.     

The Cathode Choice for Commercialization of Sodium‐Ion Batteries: Layered Transition Metal Oxides versus Prussian Blue Analogs

With the unprecedentedly increasing demand for renewable and clean energy sources, the sodium‐ion battery (SIB) is emerging as an alternative or complementary energy storage candidate to the present commercial lithium‐ion battery due to the abundance and low cost of sodium resources. Layered transition metal oxides and Prussian blue analogs are reviewed in terms of their commercial potential as cathode materials for SIBs. The recent progress in research on their half cells and full cells for the ultimate application in SIBs are summarized. In addition, their electrochemical performance, suitability for scaling up, cost, and environmental concerns are compared in detail with a brief outlook on future prospects. It is anticipated that this review will inspire further development of layered transition metal oxides and Prussian blue analogs for SIBs, especially for their emerging commercialization.     

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

Surface 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 Na_2/3[Ni_1/3Mn_2/3]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 Na_2/3[Ni_1/3Mn_2/3]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.     

Layered Oxide Cathodes Promoted by Structure Modulation Technology for Sodium‐Ion Batteries

Considering the ever‐growing climatic degeneration, sustainable and renewable energy sources are needed to be effectively integrated into the grid through large‐scale electrochemical energy storage and conversion (EESC) technologies. With regard to their competent benefit in cost and sustainable supply of resource, room‐temperature sodium‐ion batteries (SIBs) have shown great promise in EESC, triumphing over other battery systems on the market. As one of the most fascinating cathode materials due to the simple synthesis process, large specific capacity, and high ionic conductivity, Na‐based layered transition metal oxide cathodes commonly suffer from the sluggish kinetics, multiphase evolution, poor air stability, and insufficient comprehensive performance, restricting their commercialization application. Here, this review summarizes the recent advances in layered oxide cathode materials for SIBs through different optimal structure modulation technologies, with an emphasis placed on strategies to boost Na⁺ kinetics and reduce the irreversible phase transition as well as enhance the store stability. Meanwhile, a thorough and in‐depth systematical investigation of the structure–function–property relationship is also discussed, and the challenges as well as opportunities for practical application electrode materials are sketched. The insights brought forward in this review can be considered as a guide for SIBs in next‐generation EESC.     

Layered P2‐Type K0.44Ni0.22Mn0.78O2 as a High‐Performance Cathode for Potassium‐Ion Batteries

Potassium‐ion batteries (KIBs) are emerging as one of the most promising candidates for large‐scale energy storage owing to the natural abundance of the materials required for their fabrication and the fact that their intercalation mechanism is identical to that of lithium‐ion batteries. However, the larger ionic radius of K⁺ is likely to induce larger volume expansion and sluggish kinetics, resulting in low specific capacity and unsatisfactory cycle stability. A new Ni/Mn‐based layered oxide, P2‐type K_0.44Ni_0.22Mn_0.78O₂, is designed and synthesized. A cathode designed using this material delivers a high specific capacity of 125.5 mAh g^?1 at 10 mA g^?1, good cycle stability with capacity retention of 67% over 500 cycles and fast kinetic properties. In situ X‐ray diffraction recorded for the initial two cycles reveals single solid‐solution processes under P2‐type framework with small volume change of 1.5%. Moreover, a cathode electrolyte interphase layer is observed on the surface of the electrode after cycling with possible components of K₂CO₃, RCO₂K, KOR, KF, etc. A full cell using K_0.44Ni_0.22Mn_0.78O₂ as the cathode and soft carbon as the anode also exhibits exceptional performance, with capacity retention of 90% over 500 cycles as well as superior rate performance. These findings suggest P2‐K_0.44Ni_0.22Mn_0.78O₂ is a promising candidate as a high‐performance cathode for KIBs.     

Atomic Structure and Kinetics of NASICON NaxV2(PO4)3 Cathode for Sodium‐Ion Batteries

Na₃V₂(PO₄)₃ is one of the most important cathode materials for sodium‐ion batteries, delivering about two Na extraction/insertion from/into the unit structure. To understand the mechanism of sodium storage, a detailed structure of rhombohedral Na₃V₂(PO₄)₃ and its sodium extracted phase of NaV₂(PO₄)₃ are investigated at the atomic scale using a variety of advanced techniques. It is found that two different Na sites (6b, M1 and 18e, M2) with different coordination environments co‐exist in Na₃V₂(PO₄)₃, whereas only one Na site (6b, M1) exists in NaV₂(PO₄)₃. When Na is extracted from Na₃V₂(PO₄)₃ to form NaV₂(PO₄)₃, Na⁺ occupying the M2 site (CN = 8) is extracted and the rest of the Na remains at M1 site (CN = 6). In addition, the Na atoms are not randomly distributed, possibly with an ordered arrangement in M2 sites locally for Na₃V₂(PO₄)₃. Na⁺ ions at the M1 sites in Na₃V₂(PO₄)₃ tend to remain immobilized, suggesting a direct M2‐to‐M2 conduction pathway. Only Na occupying the M2 sites can be extracted, suggesting about two Na atoms able to be extracted from the Na₃V₂(PO₄)₃ structure.     

Layered P2‐Type K0.65Fe0.5Mn0.5O2 Microspheres as Superior Cathode for High‐Energy Potassium‐Ion Batteries

Potassium‐ion batteries have been regarded as the potential alternatives to lithium‐ion batteries (LIBs) due to the low cost, earth abundance, and low potential of K (?2.936 vs standard hydrogen electrode (SHE)). However, the lack of low‐cost cathodes with high energy density and long cycle life always limits its application. In this work, high‐energy layered P2‐type hierarchical K_0.65Fe_0.5Mn_0.5O₂ (P2‐KFMO) microspheres, assembled by the primary nanoparticles, are fabricated via a modified solvent‐thermal method. Benefiting from the unique microspheres with primary nanoparticles, the K⁺ intercalation/deintercalation kinetics of P2‐KFMO is greatly enhanced with a stabilized cathodic electrolyte interphase on the cathode. The P2‐KFMO microsphere presents a highly reversible potassium storage capacity of 151 mAh g^?1 at 20 mA g^?1, fast rate capability of 103 mAh g^?1 at 100 mA g^?1, and long cycling stability with 78% capacity retention after 350 cycles. A full cell with P2‐KFMO microspheres as cathode and hard carbon as anode is constructed, which exhibits long‐term cycling stability (>80% of retention after 100 cycles). The present high‐performance P2‐KFMO microsphere cathode synthesized using earth‐abundant elements provides a new cost‐effective alternative to LIBs for large‐scale energy storage.     

Hierarchical Engineering of Porous P2‐Na2/3Ni1/3Mn2/3O2 Nanofibers Assembled by Nanoparticles Enables Superior Sodium‐Ion Storage Cathodes

Layered transition metal oxides (TMOs) are appealing cathode candidates for sodium‐ion batteries (SIBs) by virtue of their facile 2D Na⁺ diffusion paths and high theoretical capacities but suffer from poor cycling stability. Herein, taking P2‐type Na_2/3Ni_1/3Mn_2/3O₂ as an example, it is demonstrated that the hierarchical engineering of porous nanofibers assembled by nanoparticles can effectively boost the reaction kinetics and stabilize the structure. The P2‐Na_2/3Ni_1/3Mn_2/3O₂ nanofibers exhibit exceptional rate capability (166.7 mA h g^?1 at 0.1 C with 73.4 mA h g^?1 at 20 C) and significantly improved cycle life (≈81% capacity retention after 500 cycles) as cathode materials for SIBs. The highly reversible structure evolution and Ni/Mn valence change during sodium insertion/extraction are verified by in operando X‐ray diffraction and ex situ X‐ray photoelectron spectroscopy, respectively. The facilitated electrode process kinetics are demonstrated by an additional study using the electrochemical measurements and density functional theory computations. More impressively, the prototype Na‐ion full battery built with a Na_2/3Ni_1/3Mn_2/3O₂ nanofibers cathode and hard carbon anode delivers a promising energy density of 212.5 Wh kg^?1. The concept of designing a fibrous framework composed of small nanograins offers a new and generally applicable strategy for enhancing the Na‐storage performance of layered TMO cathode materials.     

Understanding the Structural Evolution and Redox Mechanism of a NaFeO2–NaCoO2 Solid Solution for Sodium‐Ion Batteries

Na‐ion batteries have become promising candidates for large‐scale energy‐storage systems because of the abundant Na resources and they have attracted considerable academic interest because of their unique behavior, such as their electrochemical activity for the Fe³⁺/Fe⁴⁺ redox couple. The high‐rate performance derived from the low Lewis‐acidity of the Na⁺ ions is another advantage of Na‐ion batteries and has been demonstrated in NaFe_1/2Co_1/2O₂ solutions. Here, a solid solution of NaFeO₂‐NaCoO₂ is synthesized and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of operando X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and density functional theory (DFT) calculations for Na_{1– x} Fe_1/2Co_1/2O₂ reveals that the O3‐type phase transforms into a P3‐type phase coupled with Na⁺/vacancy ordering, which has not been observed in O3‐type NaFeO₂. The substitution of Co for Fe stabilizes the P3‐type phase formed by sodium extraction and could suppress the irreversible structural change that is usually observed in O3‐type NaFeO₂, resulting in a better cycle retention and higher rate performance. Although no ordering of the transition metal ions is seen in the neutron diffraction experiments, as supported by Monte‐Carlo simulations, the formation of a superlattice originating from the Na⁺/vacancy ordering is found by synchrotron X‐ray diffraction for Na_0.5Fe_1/2Co_1/2O₂, which may involve a potential step in the charge/discharge profiles.     

Novel Cathode Materials for Na‐Ion Batteries Composed of Spoke‐Like Nanorods of Na[Ni0.61Co0.12Mn0.27]O2 Assembled in Spherical Secondary Particles

The development of high‐energy and high‐power density sodium‐ion batteries is a great challenge for modern electrochemistry. The main hurdle to wide acceptance of sodium‐ion batteries lies in identifying and developing suitable new electrode materials. This study presents a composition‐graded cathode with average composition Na[Ni_0.61Co_0.12Mn_0.27]O₂, which exhibits excellent performance and stability. In addition to the concentration gradients of the transition metal ions, the cathode is composed of spoke‐like nanorods assembled into a spherical superstructure. Individual nanorod particles also possess strong crystallographic texture with respect to the center of the spherical particle. Such morphology allows the spoke‐like nanorods to assemble into a compact structure that minimizes its porosity and maximizes its mechanical strength while facilitating Na⁺‐ion transport into the particle interior. Microcompression tests have explicitly verified the mechanical robustness of the composition‐graded cathode and single particle electrochemical measurements have demonstrated the electrochemical stability during Na⁺‐ion insertion and extraction at high rates. These structural and morphological features contribute to the delivery of high discharge capacities of 160 mAh (g oxide)^?1 at 15 mA g^?1 (0.1 C rate) and 130 mAh g^?1 at 1500 mA g^?1 (10 C rate). The work is a pronounced step forward in the development of new Na ion insertion cathodes with a concentration gradient.     

Low‐Temperature Growth of SiO2 Films by Plasma‐Enhanced Atomic Layer Deposition

Silicon dioxide (SiO₂) films prepared by plasma‐enhanced atomic‐layer deposition were successfully grown at temperatures of 100 to 250 °C, showing self‐limiting characteristics. The growth rate decreases with an increasing deposition temperature. The relative dielectric constants of SiO₂ films are ranged from 4.5 to 7.7 with the decrease of growth temperature. A SiO₂ film grown at 250 °C exhibits a much lower leakage current than that grown at 100°C due to its high film density and the fact that it contains deeper electron traps.     

Urchin‐Like CoSe2 as a High‐Performance Anode Material for Sodium‐Ion Batteries

Urchin‐like CoSe₂ assembled by nanorods has been synthesized via simple solvothermal route and has been first applied as an anode material for sodium‐ion batteries (SIBs) with ether‐based electrolytes. The CoSe₂ delivers excellent sodiation and desodiation properties when using 1 m NaCF₃SO₃ in diethyleneglycol dimethylether as an electrolyte and cycling between 0.5 and 3.0 V. A high discharge capacity of 0.410 Ah g^?1 is obtained at 1 A g^?1 after 1800 cycles, corresponding to a capacity retention of 98.6% calculated from the 30th cycle. Even at an ultrahigh rate of 50 A g^?1, the capacity still maintains 0.097 Ah g^?1. The reaction mechanism of the as‐prepared CoSe₂ is also investigated. The results demonstrate that at discharged 1.56 V, insertion reaction occurs, while two conversion reactions take place at the second and third plateaus around 0.98 and 0.65 V. During the charge process, Co first reacts with Na₂Se to form Na_xCoSe₂ and then turns back to CoSe₂. In addition to Na/CoSe₂ half cells, Na₃V₂(PO₄)₃/CoSe₂ full cell with excessive amount of Na₃V₂(PO₄)₃ has been studied. The full cell exhibits a reversible capacity of 0.380 Ah g^?1. This work definitely enriches the possibilities for anode materials for SIBs with high performance.     

Microstructure Evolution of Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium‐Ion Batteries

Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni_0.75Co_0.10Mn_0.15]O₂ is performed starting from its hydroxide precursor, FCG [Ni_0.75Co_0.10Mn_0.15](OH)₂ prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)₂, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)₂. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.     

General Synthesis of Dual Carbon‐Confined Metal Sulfides Quantum Dots Toward High‐Performance Anodes for Sodium‐Ion Batteries

Sponge‐like composites assembled by cobalt sulfides quantum dots (Co₉S₈ QD), mesoporous hollow carbon polyhedral (HCP) matrix, and a reduced graphene oxide (rGO) wrapping sheets are synthesized by a simultaneous thermal reduction, carbonization, and sulfidation of zeolitic imidazolate frameworks@GO precursors. Specifically, Co₉S₈ QD with size less than 4 nm are homogenously embedded within HCP matrix, which is encapsulated in macroporous rGO, thereby leading to the double carbon‐confined hierarchical composites with strong coupling effect. Experimental data combined with density functional theory calculations reveal that the presence of coupled rGO not only prevents the aggregation and excessive growth of particles, but also expands the lattice parameters of Co₉S₈ crystals, enhancing the reactivity for sodium storage. Benefiting from the hierarchical porosity, conductive network, structural integrity, and a synergistic effect of the components, the sponge‐like composites used as binder‐free anodes manifest outstanding sodium‐storage performance in terms of excellent stable capacity (628 mAh g^?1 after 500 cycles at 300 mA g^?1) and exceptional rate capability (529, 448, and 330 mAh g^?1 at 1600, 3200, and 6400 mA g^?1). More importantly, the synthetic method is very versatile and can be easily extended to fabricate other transition‐metal‐sulfides‐based sponge‐like composites with excellent electrochemical performances.     

Freestanding Metallic 1T MoS2 with Dual Ion Diffusion Paths as High Rate Anode for Sodium‐Ion Batteries

This work studies for the first time the metallic 1T MoS₂ sandwich grown on graphene tube as a freestanding intercalation anode for promising sodium‐ion batteries (SIBs). Sodium is earth‐abundant and readily accessible. Compared to lithium, the main challenge of sodium‐ion batteries is its sluggish ion diffusion kinetic. The freestanding, porous, hollow structure of the electrode allows maximum electrolyte accessibility to benefit the transportation of Na⁺ ions. Meanwhile, the metallic MoS₂ provides excellent electron conductivity. The obtained 1T MoS₂ electrode exhibits excellent electrochemical performance: a high reversible capacity of 313 mAh g^?1 at a current density of 0.05 A g^?1 after 200 cycles and a high rate capability of 175 mAh g^?1 at 2 A g^?1. The underlying mechanism of high rate performance of 1T MoS₂ for SIBs is the high electrical conductivity and excellent ion accessibility. This study sheds light on using the 1T MoS₂ as a novel anode for SIBs.     

Few‐Layer MoSe2 Nanosheets with Expanded (002) Planes Confined in Hollow Carbon Nanospheres for Ultrahigh‐Performance Na‐Ion Batteries

Sodium‐ion batteries (SIBs) are considered as a promising alternative to lithium‐ion batteries, due to the abundant reserves and low price of Na sources. To date, the development of anode materials for SIBs is still confronted with many serious problems. In this work, encapsulation‐type structured MoSe₂@hollow carbon nanosphere (HCNS) materials assembled with expanded (002) planes few‐layer MoSe₂ nanosheets confined in HCNS are successfully synthesized through a facile strategy. Notably, the interlayer spacing of the (002) planes is expanded to 1.02 nm, which is larger than the intrinsic value of pristine MoSe₂ (0.64 nm). Furthermore, the few‐layer nanosheets are space‐confined in the inner cavity of the HCNS, forming hybrid MoSe₂@HCNS structures. When evaluated as anode materials for SIBs, it shows excellent rate capabilities, ultralong cycling life with exceptional Coulombic efficiency even at high current density, maintaining 501 and 471 mA h g^?1 over 1000 cycles at 1 and 3 A g^?1, respectively. Even when cycled at current densities as high as 10 A g^?1, a capacity retention of 382 mA h g^?1 can be achieved. The expanded (002) planes, 2D few‐layer nanosheets, and unique carbon shell structure are responsible for the ultralong cycling and high rate performance.     

Engineering Solid Electrolyte Interphase for Pseudocapacitive Anatase TiO2 Anodes in Sodium‐Ion Batteries

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.