Genetic and clinical characteristics of primary hemophagocytic lymphohistiocytosis in children.

To analyze the genetic variation and prognosis of primary hemophagocytic lymphohistiocytosis (pHLH) in children and the clinical features of isolated central nervous system HLH (CNS-HLH). We retrospectively analyzed the clinical and genetic data of 480 HLH children admitted to our hospital from September 2017 to September 2022. There were 66 patients (13.75%) with pHLH, and the median age was 3.21 years (0.17-12.92 years). Variants in UNC13D (22/66, 33.33%), PRF1 (20/66, 30.30%) and XIAP (11/66, 16.67%) were the most common. More CNS involvement was observed in pHLH patients than in secondary hemophagocytic lymphohistiocytosis (sHLH) patients (50% vs. 25.3%, P = 0.001). Eight pHLH patients had isolated CNS-HLH at onset, which progressed to systemic HLH within 10-30 days to several years. Among them, five patients who underwent hematopoietic stem cell transplantation (HSCT) survived without CNS sequelae, and the three patients who did not undergo HSCT died of disease progression or recurrence. Determination of natural killer (NK) cell cytotoxicity and CD107a levels had low sensitivity and specificity in the diagnosis of pHLH, especially in patients with PRF1 and XIAP mutations. The 3-year overall survival (OS) was significantly lower in pHLH patients than in sHLH patients (74.5% ± 14.7% vs. 89.2% ± 3.53%, P = 0.021) and in patients with CNS involvement than in those without (53.8% ± 26.07% vs. 94.4% ± 10.58%, P = 0.012). There was a significant difference in OS among pHLH patients with different gene variants (P = 0.032); patients with PRF1 variants had poor 3-year OS, and patients with XIAP variants had good 3-year OS (50% ± 28.22% and 100%, respectively). pHLH patients with distinct variants have different prognoses. Isolated CNS-HLH patients are easily misdiagnosed, and HSCT may be beneficial for these patients. Determination of NK cell cytotoxicity and CD107a levels cannot precisely distinguish pHLH from sHLH.

From Liquid to Solid-State Batteries: Li-Rich Mn-Based Layered Oxides as Emerging Cathodes with High Energy Density.

Li-rich Mn-based (LRMO) cathode materials have attracted widespread attention due to their high specific capacity, energy density, and cost-effectiveness. However, challenges such as poor cycling stability, voltage deca,y and oxygen escape limit their commercial application in liquid Li-ion batteries. Consequently, there is a growing interest in the development of safe and resilient all-solid-state batteries (ASSBs), driven by their remarkable safety features and superior energy density. ASSBs based on LRMO cathodes offer distinct advantages over conventional liquid Li-ion batteries, including long-term cycle stability, thermal and wider electrochemical windows stability, as well as the prevention of transition metal dissolution. This review aims to recapitulate the challenges and fundamental understanding associated with the application of LRMO cathodes in ASSBs. Additionally, it proposes the mechanisms of interfacial mechanical and chemical instability, introduces noteworthy strategies to enhance oxygen redox reversibility, enhances high-voltage interfacial stability, and optimizes Li+ transfer kinetics. Furthermore, it suggests potential research approaches to facilitate the large-scale implementation of LRMO cathodes in ASSBs.

Probing the Origin of Viscosity of Liquid Electrolytes for Lithium Batteries.

Viscosity is an extremely important property for ion transport and wettability of electrolytes. Easy access to viscosity values and a deep understanding of this property remain challenging yet critical to evaluating the electrolyte performance and tailoring electrolyte recipes with targeted properties. We proposed a screened overlapping method to efficiently compute the viscosity of lithium battery electrolytes by molecular dynamics simulations. The origin of electrolyte viscosity was further comprehensively probed. The viscosity of solvents exhibits a positive correlation with the binding energy between molecules, indicating viscosity is directly correlated to intermolecular interactions. Salts in electrolytes enlarge the viscosity significantly with increasing concentrations while diluents serve as the viscosity reducer, which is attributed to the varied binding strength from cation-anion and cation-solvent associations. This work develops an accurate and efficient method for computing the electrolyte viscosity and affords deep insight into viscosity at the molecular level, which exhibits the huge potential to accelerate advanced electrolyte design for next-generation rechargeable batteries.

Research Progresses of Liquid Electrolytes in Lithium-Ion Batteries.

In recent years, the rapid development of modern society is calling for advanced energy storage to meet the growing demands of energy supply and generation. As one of the most promising energy storage systems, secondary batteries are attracting much attention. The electrolyte is an important part of the secondary battery, and its composition is closely related to the electrochemical performance of the secondary batteries. Lithium-ion battery electrolyte is mainly composed of solvents, additives, and lithium salts, which are prepared according to specific proportions under certain conditions and according to the needs of characteristics. This review analyzes the advantages and current problems of the liquid electrolytes in lithium-ion batteries (LIBs) from the mechanism of action and failure mechanism, summarizes the research progress of solvents, lithium salts, and additives, analyzes the future trends and requirements of lithium-ion battery electrolytes, and points out the emerging opportunities in advanced lithium-ion battery electrolytes development.

Eliminating interfacial O-involving degradation in Li-rich Mn-based cathodes for all-solid-state lithium batteries.

In the pursuit of energy-dense all-solid-state lithium batteries (ASSBs), Li-rich Mn-based oxide (LRMO) cathodes provide an exciting path forward with unexpectedly high capacity, low cost, and excellent processibility. However, the cause for LRMO|solid electrolyte interfacial degradation remains a mystery, hindering the application of LRMO-based ASSBs. Here, we first reveal that the surface oxygen instability of LRMO is the driving force for interfacial degradation, which severely blocks the interfacial Li-ion transport and triggers fast battery failure. By replacing the charge compensation of surface oxygen with sulfite, the overoxidation and interfacial degradation can be effectively prevented, therefore achieving a high specific capacity (~248 mAh g-1, 1.1 mAh cm-2; ~225 mAh g-1, 2.9 mAh cm-2) and excellent long-term cycling stability of >300 cycles with 81.2% capacity retention at room temperature. These findings emphasize the importance of irreversible anion reactions in interfacial failure and provide fresh insights into constructing stable interfaces in LRMO-based ASSBs.

The void formation behaviors in working solid-state Li metal batteries.

The fundamental understanding of the elusive evolution behavior of the buried solid-solid interfaces is the major barrier to exploring solid-state electrochemical devices. Here, we uncover the interfacial void evolution principles in solid-state batteries, build a solid-state void nucleation and growth model, and make an analogy with the bubble formation in liquid phases. In solid-state lithium metal batteries, the lithium stripping-induced interfacial void formation determines the morphological instabilities that result in battery failure. The void-induced contact loss processes are quantified in a phase diagram under wide current densities ranging from 1.0 to 10.0 milliamperes per square centimeter by rational electrochemistry calculations. The in situ-visualized morphological evolutions reveal the microscopic features of void defects under different stripping circumstances. The electrochemical-morphological relationship helps to elucidate the current density- and areal capacity-dependent void nucleation and growth mechanisms, which affords fresh insights on understanding and designing solid-solid interfaces for advanced solid-state batteries.

Effect of sports fatigue on plantar pressure distribution of healthy male college students / Efeito da fadiga esportiva na distribuição da pressão plantar de estudantes universitários masculinos saudáveis / Efecto de la fatiga deportiva sobre la distribución de la presión plantar en estudiantes universitarios masculinos saludables

ABSTRACT Objective: To understand the influence of sports fatigue on plantar pressure distribution of healthy male college students and provide a theoretical basis for improving their awareness of foot health. Methods: Forty-nine ordinary male college students jogged along the 800-meter runway to moderate fatigue. All the subjects took off their shoes and socks and walked naturally with their usual gait. The dynamic plantar pressure of each foot was measured twice in one step. FootscanUSB2 Belgian flat-plate plantar pressure testing system was used for testing. Results: The average dynamic peak plantar pressure was (206.38 44.59) N for boys, and the changes of AA and CB walking speed in the arch did not change significantly. After fatigue, the peak pressure of FM, AA, RH5 in left foot and FM, AA, CB in right foot decreased significantly (P < 0.05, P < 0.01). The peak time of RH and CB in the left foot was significantly shorter than that before fatigue (P < 0.05, P < 0.01), while FMF, AA, C areas had no significant change but tended to be delayed. There were significant differences in peak force-time between boys' left and right feet except for the fifth metatarsal bone (P < 0.05). There is a significant difference in the peak force-time between the second and fifth toes of the left foot (P< 0.01), and there is a gender difference in the peak force-time between the second metatarsal and the third metatarsal (P < 0.05). Conclusion: Sports fatigue leads to the decrease of physiological functions such as muscle strength of lower limbs, which leads to the corresponding changes in gait stages, plantar pressure distribution parameters, and foot balance. Level of evidence II; Therapeutic studies - investigation of treatment results.

RESUMO Objetivo: Entender a influência da fadiga esportiva na distribuição da pressão plantar de estudantes universitários masculinos saudáveis e fornecer uma base teórica para melhorar sua consciência sobre a saúde dos pés. Métodos: Quarenta e nove estudantes universitários masculinos comuns correram ao longo da pista de 800 metros para moderar a fadiga. Todos os sujeitos tiraram seus sapatos e meias e caminharam naturalmente com sua marcha habitual. A pressão plantar dinâmica de cada pé foi medida duas vezes em um único passo. O sistema de teste de pressão plantar de placa plana belga FootscanUSB2 foi usado para testes. Resultados: A pressão plantar dinâmica média de pico foi (206.38 44.59) N para meninos, e as alterações de velocidade de caminhada AA e CB no arco não mudaram significativamente. Após a fadiga, a pressão de pico de FM, AA, RH5 no pé esquerdo e FM, AA, CB no pé direito diminuiu significativamente (P < 0,05, P < 0,01). O tempo de pico de RH e CB no pé esquerdo foi significativamente menor do que antes da fadiga (P < 0,05, P < 0,01), enquanto as áreas FMF, AA, C não tiveram nenhuma mudança significativa, mas tenderam a ser atrasadas. Havia diferenças significativas no tempo de pico de força entre o pé esquerdo e direito dos meninos, exceto para o quinto metatarso (P < 0,05). Houve uma diferença significativa no tempo de pico de força entre o segundo e o quinto dedos do pé esquerdo (P< 0,01), e há uma diferença de gênero no tempo de pico de força entre o segundo metatarso e o terceiro metatarso (P < 0,05). Conclusão: A fadiga esportiva leva à diminuição das funções fisiológicas, tais como a força muscular dos membros inferiores, o que leva às mudanças correspondentes nos estágios de marcha, parâmetros de distribuição da pressão plantar e equilíbrio do pé. Nível de evidência II; Estudos terapêuticos - investigação de resultados de tratamento.

RESUMEN Objetivo: Comprender la influencia de la fatiga deportiva en la distribución de la presión plantar de los estudiantes universitarios varones sanos y proporcionar una base teórica para mejorar su conciencia sobre la salud de los pies. Métodos: Cuarenta y nueve estudiantes universitarios varones normales trotaron a lo largo de una pista de 800 metros hasta alcanzar una fatiga moderada. Todos los sujetos se quitaron los zapatos y los calcetines y caminaron de forma natural con su marcha habitual. Se midió la presión plantar dinámica de cada pie dos veces en un único paso. Para las pruebas se utilizó el sistema belga de pruebas de presión plantar FootscanUSB2. Resultados: El promedio de la presión plantar dinámica máxima fue de (206.38 44.59) N para los niños, y los cambios de la velocidad de marcha AA y CB en el arco no cambiaron significativamente. Después de la fatiga, la presión máxima de FM, AA, RH5 en el pie izquierdo y de FM, AA, CB en el pie derecho disminuyó significativamente (P < 0,05, P < 0,01). El tiempo de pico de RH y CB en el pie izquierdo fue significativamente menor que antes de la fatiga (P < 0,05, P < 0,01), mientras que las áreas FMF, AA, C no tuvieron cambios significativos, pero tendieron a retrasarse. Hubo diferencias significativas en el pico de fuerza-tiempo entre los pies izquierdo y derecho de los niños, excepto en el quinto hueso metatarsiano (P < 0,05). Hay una diferencia significativa en el pico de fuerza-tiempo entre el segundo y el quinto dedo del pie izquierdo (P < 0,01), y hay una diferencia de género en el pico de fuerza-tiempo entre el segundo metatarsiano y el tercer metatarsiano (P < 0,05). Conclusión: La fatiga deportiva conduce a la disminución de funciones fisiológicas como la fuerza muscular de los miembros inferiores, lo que conlleva los correspondientes cambios en las fases de la marcha, los parámetros de distribución de la presión plantar y el equilibrio del pie. Nivel de evidencia II; Estudios terapéuticos - investigación de resultados de tratamiento.

Thermal Runaway of Nonflammable Localized High-Concentration Electrolytes for Practical LiNi0.8 Mn0.1 Co0.1 O2 |Graphite-SiO Pouch Cells.

With continuous improvement of batteries in energy density, enhancing their safety is becoming increasingly urgent. Herein, practical high energy density LiNi0.8 Mn0.1 Co0.1 O2 |graphite-SiO pouch cell with nonflammable localized high concentration electrolyte (LHCE) is proposed that presents unique self-discharge characteristic before thermal runaway (TR), thus effectively reducing safety hazards. Compared with the reference electrolyte, pouch cell with nonflammable LHCE can increase self-generated heat temperature by 4.4 °C, increase TR triggering temperature by 47.3 °C, decrease the TR highest temperature by 71.8 °C, and extend the time from self-generated heat to triggering TR by ≈8 h. In addition, the cell with nonflammable LHCE presents superior high voltage cycle stability, attributed to the formation of robust inorganic-rich electrode-electrolyte interphase. The strategy represents a pivotal step forward for practical high energy and high safety batteries.

Inhibiting intercrystalline reactions of anode with electrolytes for long-cycling lithium batteries.

The life span of lithium batteries as energy storage devices is plagued by irreversible interfacial reactions between reactive anodes and electrolytes. Occurring on polycrystal surface, the reaction process is inevitably affected by the surface microstructure of anodes, of which the understanding is imperative but rarely touched. Here, the effect of grain boundary of lithium metal anodes on the reactions was investigated. The reactions preferentially occur at the grain boundary, resulting in intercrystalline reactions. An aluminum (Al)-based heteroatom-concentrated grain boundary (Al-HCGB), where Al atoms concentrate at grain boundary, was designed to inhibit the intercrystalline reactions. In particular, the scalable preparation of Al-HCGB was demonstrated, with which the cycling performance of a pouch cell (355 Wh kg-1) was significantly improved. This work opens a new avenue to explore the effect of the surface microstructure of anodes on the interfacial reaction process and provides an effective strategy to inhibit reactions between anodes and electrolytes for long-life-span practical lithium batteries.

The carrier transition from Li atoms to Li vacancies in solid-state lithium alloy anodes.

The stable cycling of energy-dense solid-state batteries is highly relied on the kinetically stable solid-state Li alloying reactions. The Li metal precipitation at solid-solid interfaces is the primary cause of interface fluctuations and battery failures, whose formation requires a clear mechanism interpretation, especially on the key kinetic short board. Here, we introduce the lithium alloy anode as a model system to quantify the Li kinetic evolution and transition from the alloying reaction to the metal deposition in solid-state batteries, identifying that there is a carrier transition from Li atoms to Li vacancies during lithiation processes. The rate-determining step is charge transfer or Li atom diffusion at different lithiation stages.

Lithium Bonds in Lithium Batteries.

Lithium bonds are analogous to hydrogen bonds and are therefore expected to exhibit similar characteristics and functions. Additionally, the metallic nature and large atomic radius of Li bestow the Li bond with special features. As one of the most important applications of the element, Li batteries afford emerging opportunities for the exploration of Li bond chemistry. Herein, the historical development and concept of the Li bond are reviewed, in addition to the application of Li bonds in Li batteries. In this way, a comprehensive understanding of the Li bond in Li batteries and an outlook on its future developments is presented.

Rechargeable Lithium Metal Batteries with an In-Built Solid-State Polymer Electrolyte and a High Voltage/Loading Ni-Rich Layered Cathode.

Solid-state batteries enabled by solid-state polymer electrolytes (SPEs) are under active consideration for their promise as cost-effective platforms that simultaneously support high-energy and safe electrochemical energy storage. The limited oxidative stability and poor interfacial charge transport in conventional polymer electrolytes are well known, but difficult challenges must be addressed if high-voltage intercalating cathodes are to be used in such batteries. Here, ether-based electrolytes are in situ polymerized by a ring-opening reaction in the presence of aluminum fluoride (AlF3 ) to create SPEs inside LiNi0.6 Co0.2 Mn0.2 O2 (NCM) || Li batteries that are able to overcome both challenges. AlF3 plays a dual role as a Lewis acid catalyst and for the building of fluoridized cathode-electrolyte interphases, protecting both the electrolyte and aluminum current collector from degradation reactions. The solid-state NCM || Li metal batteries exhibit enhanced specific capacity of 153 mAh g-1 under high areal capacity of 3.0 mAh cm-2 . This work offers an important pathway toward solid-state polymer electrolytes for high-voltage solid-state batteries.

Dual-Phase Single-Ion Pathway Interfaces for Robust Lithium Metal in Working Batteries.

The lithium (Li) metal anode is confronted by severe interfacial issues that strongly hinder its practical deployment. The unstable interfaces directly induce unfavorable low cycling efficiency, dendritic Li deposition, and even strong safety concerns. An advanced artificial protective layer with single-ion pathways holds great promise for enabling a spatially homogeneous ionic and electric field distribution over Li metal surface, therefore well protecting the Li metal anode during long-term working conditions. Herein, a robust dual-phase artificial interface is constructed, where not only the single-ion-conducting nature, but also high mechanical rigidity and considerable deformability can be fulfilled simultaneously by the rational integration of a garnet Al-doped Li6.75 La3 Zr1.75 Ta0.25 O12 -based bottom layer and a lithiated Nafion top layer. The as-constructed artificial solid electrolyte interphase is demonstrated to significantly stabilize the repeated cell charging/discharging process via regulating a facile Li-ion transport and a compact Li plating behavior, hence contributing to a higher coulombic efficiency and a considerably enhanced cyclability of lithium metal batteries. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and affords fresh insights into achieving dendrite-free Li deposition behavior in a working battery.

Fast Charging Lithium Batteries: Recent Progress and Future Prospects.

Fast charging enables electronic devices to be charged in a very short time, which is essential for next-generation energy storage systems. However, the increase of safety risks and low coulombic efficiency resulting from fast charging severely hamper the practical applications of this technology. This Review summarizes the challenges and recent progress of lithium batteries for fast charging. First, it describes the definition of fast charging and proposes a critical value of ionic and electrical conductivity of electrodes for fast charging in a working battery. Then based on this definition, the requirements and optimization strategies of the electrode, electrolyte, and electrode/electrolyte interface for fast charging are proposed. Finally, a general conclusion and perspectives on the better understanding of lithium batteries with fast charging capability are presented.

An ion redistributor for dendrite-free lithium metal anodes.

Lithium (Li) metal anodes have attracted considerable interest due to their ultrahigh theoretical gravimetric capacity and very low redox potential. However, the issues of nonuniform lithium deposits (dendritic Li) during cycling are hindering the practical applications of Li metal batteries. Herein, we propose a concept of ion redistributors to eliminate dendrites by redistributing Li ions with Al-doped Li6.75La3Zr1.75Ta0.25O12 (LLZTO) coated polypropylene (PP) separators. The LLZTO with three-dimensional ion channels can act as a redistributor to regulate the movement of Li ions, delivering a uniform Li ion distribution for dendrite-free Li deposition. The standard deviation of ion concentration beneath the LLZTO composite separator is 13 times less than that beneath the routine PP separator. A Coulombic efficiency larger than 98% over 450 cycles is achieved in a Li | Cu cell with the LLZTO-coated separator. This approach enables a high specific capacity of 140 mAh g-1 for LiFePO4 | Li pouch cells and prolonged cycle life span of 800 hours for Li | Li pouch cells, respectively. This strategy is facile and efficient in regulating Li-ion deposition by separator modifications and is a universal method to protect alkali metal anodes in rechargeable batteries.

The Radical Pathway Based on a Lithium-Metal-Compatible High-Dielectric Electrolyte for Lithium-Sulfur Batteries.

High-dielectric solvents were explored for enhancing the sulfur utilization in lithium-sulfur (Li-S) batteries, but their applications have been impeded by low stability at the lithium metal anode. Now a radical-directed, lithium-compatible, and strongly polysulfide-solvating high-dielectric electrolyte based on tetramethylurea is presented. Over 200 hours of cycling was realized in Li|Li symmetric cells, showing good compatibility of the tetramethylurea-based electrolyte with lithium metal. The high solubility of short-chain polysulfides, as well as the presence of active S3 .- radicals, enabled pouch cells to deliver a discharge capacity of 1524 mAh g-1 and an energy density of 324 Wh kg-1 . This finding suggests an alternative recipe to ether-based electrolytes for Li-S batteries.

An anion-immobilized composite electrolyte for dendrite-free lithium metal anodes.

Lithium metal is strongly regarded as a promising electrode material in next-generation rechargeable batteries due to its extremely high theoretical specific capacity and lowest reduction potential. However, the safety issue and short lifespan induced by uncontrolled dendrite growth have hindered the practical applications of lithium metal anodes. Hence, we propose a flexible anion-immobilized ceramic-polymer composite electrolyte to inhibit lithium dendrites and construct safe batteries. Anions in the composite electrolyte are tethered by a polymer matrix and ceramic fillers, inducing a uniform distribution of space charges and lithium ions that contributes to a dendrite-free lithium deposition. The dissociation of anions and lithium ions also helps to reduce the polymer crystallinity, rendering stable and fast transportation of lithium ions. Ceramic fillers in the electrolyte extend the electrochemically stable window to as wide as 5.5 V and provide a barrier to short circuiting for realizing safe batteries at elevated temperature. The anion-immobilized electrolyte can be applied in all-solid-state batteries and exhibits a small polarization of 15 mV. Cooperated with LiFePO4 and LiNi0.5Co0.2Mn0.3O2 cathodes, the all-solid-state lithium metal batteries render excellent specific capacities of above 150 mAh⋅g-1 and well withstand mechanical bending. These results reveal a promising opportunity for safe and flexible next-generation lithium metal batteries.

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applications is included. A general conclusion and a perspective on the current limitations and recommended future research directions of lithium metal batteries are presented. The review concludes with an attempt at summarizing the theoretical and experimental achievements in lithium metal anodes and endeavors to realize the practical applications of lithium metal batteries.

Healing High-Loading Sulfur Electrodes with Unprecedented Long Cycling Life: Spatial Heterogeneity Control.

Self-healing capability helps biological systems to maintain their survivability and extend their lifespan. Similarly, self-healing is also beneficial to next-generation secondary batteries because high-capacity electrode materials, especially the cathodes such as oxygen or sulfur, suffer from shortened cycle lives resulting from irreversible and unstable phase transfer. Herein, by mimicking a biological self-healing process, fibrinolysis, we introduced an extrinsic healing agent, polysulfide, to enable the stable operation of sulfur microparticle (SMiP) cathodes. An optimized capacity (∼3.7 mAh cm-2) with almost no decay after 2000 cycles at a high sulfur loading of 5.6 mg(S) cm-2 was attained. The inert SMiP is activated by the solubilization effect of polysulfides whereas the unstable phase transfer is mediated by mitigated spatial heterogeneity of polysulfides, which induces uniform nucleation and growth of solid compounds. The comprehensive understanding of the healing process, as well as of the spatial heterogeneity, could further guide the design of novel healing agents (e.g., lithium iodine) toward high-performance rechargeable batteries.

A Review of Solid Electrolyte Interphases on Lithium Metal Anode.

Lithium metal batteries (LMBs) are among the most promising candidates of high-energy-density devices for advanced energy storage. However, the growth of dendrites greatly hinders the practical applications of LMBs in portable electronics and electric vehicles. Constructing stable and efficient solid electrolyte interphase (SEI) is among the most effective strategies to inhibit the dendrite growth and thus to achieve a superior cycling performance. In this review, the mechanisms of SEI formation and models of SEI structure are briefly summarized. The analysis methods to probe the surface chemistry, surface morphology, electrochemical property, dynamic characteristics of SEI layer are emphasized. The critical factors affecting the SEI formation, such as electrolyte component, temperature, current density, are comprehensively debated. The efficient methods to modify SEI layer with the introduction of new electrolyte system and additives, ex-situ-formed protective layer, as well as electrode design, are summarized. Although these works afford new insights into SEI research, robust and precise routes for SEI modification with well-designed structure, as well as understanding of the connection between structure and electrochemical performance, is still inadequate. A multidisciplinary approach is highly required to enable the formation of robust SEI for highly efficient energy storage systems.