Controllable Solid Electrolyte Interphase in Nickel‐Rich Cathodes by an Electrochemical Rearrangement for Stable Lithium‐Ion Batteries

The layered nickel‐rich materials have attracted extensive attention as a promising cathode candidate for high‐energy density lithium‐ion batteries (LIBs). However, they have been suffering from inherent structural and electrochemical degradation including severe capacity loss at high electrode loading density (>3.0 g cm^?3) and high temperature cycling (>60 °C). In this study, an effective and viable way of creating an artificial solid–electrolyte interphase (SEI) layer on the cathode surface by a simple, one‐step approach is reported. It is found that the initial artificial SEI compounds on the cathode surface can electrochemically grow along grain boundaries by reacting with the by‐products during battery cycling. The developed nickel‐rich cathode demonstrates exceptional capacity retention and structural integrity under industrial electrode fabricating conditions with the electrode loading level of ≈12 mg cm^?2 and density of ≈3.3 g cm^?3. This finding could be a breakthrough for the LIB technology, providing a rational approach for the development of advanced cathode materials.     

Potassium‐Based Dual Ion Battery with Dual‐Graphite Electrode

A potassium ion battery has potential applications for large scale electric energy storage systems due to the abundance and low cost of potassium resources. Dual graphite batteries, with graphite as both anode and cathode, eliminate the use of transition metal compounds and greatly lower the overall cost. Herein, combining the merits of the potassium ion battery and dual graphite battery, a potassium‐based dual ion battery with dual‐graphite electrode is developed. It delivers a reversible capacity of 62 mA h g^?1 and medium discharge voltage of ≈3.96 V. The intercalation/deintercalation mechanism of K⁺ and PF₆^? into/from graphite is proposed and discussed in detail, with various characterizations to support.     

Water‐Soluble Sericin Protein Enabling Stable Solid–Electrolyte Interphase for Fast Charging High Voltage Battery Electrode

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) is the most promising cathode material for achieving high energy density lithium‐ion batteries attributed to its high operating voltage (≈4.75 V). However, at such high voltage, the commonly used battery electrolyte is suffered from severe oxidation, forming unstable solid–electrolyte interphase (SEI) layers. This would induce capacity fading, self‐discharge, as well as inferior rate capabilities for the electrode during cycling. This work first time discovers that the electrolyte oxidation is effectively negated by introducing an electrochemically stable silk sericin protein, which is capable to stabilize the SEI layer and suppress the self‐discharge behavior for LNMO. In addition, robust mechanical support of sericin coating maintains the structural integrity during the fast charging/discharging process. Benefited from these merits, the sericin‐based LNMO electrode possesses a much lower Li‐ion diffusion energy barrier (26.1 kJ mol⁻¹) for than that of polyvinylidene fluoride‐based LNMO electrode (37.5 kJ mol⁻¹), delivering a remarkable high‐rate performance. This work heralds a new paradigm for manipulating interfacial chemistry of electrode to solve the key obstacle for LNMO commercialization, opening a powerful avenue for unlocking the current challenges for a wide family of high operating voltage cathode materials (>4.5 V) toward practical applications.     

Polarity‐Switchable Symmetric Graphite Batteries with High Energy and High Power Densities

Multifunctional batteries with enhanced safety performance have received considerable attention for their applications at extreme conditions. However, few batteries can endure a mix‐up of battery polarity during charging, a common wrong operation of rechargeable batteries. Herein, a polarity‐switchable battery based on the switchable intercalation feature of graphite is demonstrated. The unique redox‐amphoteric intercalation behavior of graphite allows a reversible switching of graphite between anode and cathode, thus enabling polarity‐switchable symmetric graphite batteries. The large potential gap between anion and cation intercalation delivers a high midpoint device voltage (≈average voltage) of ≈4.5 V. Further, both the graphite anode and cathode are kinetically activated during the polarity switching. Consequently, polarity‐switchable symmetric graphite batteries exhibit a remarkable cycling stability (96% capacity retention after 500 cycles), a high power density of 8.66 kW kg^?1, and a high energy density of 227 Wh kg^?1 (calculated based on the total weight of active materials in both anode and cathode), which are superior to other symmetric batteries and recently reported dual‐graphite or dual‐carbon batteries. This work will inspire the development of new multifunctional energy‐storage devices based on novel materials and electrolyte systems.     

A Novel Potassium‐Ion‐Based Dual‐Ion Battery

In this work, combining both advantages of potassium‐ion batteries and dual‐ion batteries, a novel potassium‐ion‐based dual‐ion battery (named as K‐DIB) system is developed based on a potassium‐ion electrolyte, using metal foil (Sn, Pb, K, or Na) as anode and expanded graphite as cathode. When using Sn foil as the anode, the K‐DIB presents a high reversible capacity of 66 mAh g^?1 at a current density of 50 mA g^?1 over the voltage window of 3.0–5.0 V, and exhibits excellent long‐term cycling performance with 93% capacity retention for 300 cycles. Moreover, as the Sn foil simultaneously acts as the anode material and the current collector, dead load and dead volume of the battery can be greatly reduced, thus the energy density of the K‐DIB is further improved. It delivers a high energy density of 155 Wh kg^?1 at a power density of 116 W kg^?1, which is comparable with commercial lithium‐ion batteries. Thus, with the advantages of environmentally friendly, cost effective, and high energy density, this K‐DIB shows attractive potential for future energy storage application.     

Self‐Activating,Capacitive Anion Intercalation Enables High‐Power Graphite Cathodes

Developing high‐power cathodes is crucial to construct next‐generation quick‐charge batteries for electric transportation and grid applications. However, this mainly relies on nanoengineering strategies at the expense of low scalability and high battery cost. Another option is provided herein to build high‐power cathodes by exploiting inexpensive bulk graphite as the active electrode material, where anion intercalation is involved. With the assistance of a strong alginate binder, the disintegration problem of graphite cathodes due to the large volume variation of >130% is well suppressed, making it possible to investigate the intrinsic electrochemical behavior and to elucidate the charge storage kinetics of graphite cathodes. Ultrahigh power capability up to 42.9 kW kg^?1 at the energy density of >300 Wh kg^?1 (based on graphite mass) and long cycling life over 10 000 cycles are achieved, much higher than those of conventional cathode materials for Li‐ion batteries. A self‐activating and capacitive anion intercalation into graphite is discovered for the first time, making graphite a new intrinsic intercalation‐pseudocapacitance cathode material. The finding highlights the kinetical difference of anion intercalation (as cathode) from cation intercalation (as anode) into graphitic carbon materials, and new high‐power energy storage devices will be inspired.     

Tuning the Solid Electrolyte Interphase for Selective Li‐ and Na‐Ion Storage in Hard Carbon

Solid‐electrolyte interphase (SEI) films with controllable properties are highly desirable for improving battery performance. In this paper, a combined experimental and theoretical approach is used to study SEI films formed on hard carbon in Li‐ and Na‐ion batteries. It is shown that a stable SEI layer can be designed by precycling an electrode in a desired Li‐ or Na‐based electrolyte, and that ionic transport can be kinetically controlled. Selective Li‐ and Na‐based SEI membranes are produced using Li‐ or Na‐based electrolytes, respectively. The Na‐based SEI allows easy transport of Li ions, while the Li‐based SEI shuts off Na‐ion transport. Na‐ion storage can be manipulated by tuning the SEI layer with film‐forming electrolyte additives, or by preforming an SEI layer on the electrode surface. The Na specific capacity can be controlled to < 25 mAh g^?1; ≈ 1/10 of the normal capacity (250 mAh g^?1). Unusual selective/preferential transport of Li ions is demonstrated by preforming an SEI layer on the electrode surface and corroborated with a mixed electrolyte. This work may provide new guidance for preparing good ion‐selective conductors using electrochemical approaches.     

A carbonate-free,sulfone-based electrolyte for high-voltage Li-ion batteries

Practical implementation of next-generation Li-ion battery chemistries is to a large extent obstructed by the absence of an electrolyte that is capable of simultaneously supporting reversible electrochemical reactions at two extreme electrochemical potentials—above 4.5?V at the positive electrode and near 0?V vs. Li at the negative electrode. Electrolytes based on carbonate esters have been reliable in satisfying state-of-the-art Li-ion battery (LIB) chemistries below <4.2?V; however, it is the intrinsic thermodynamic tendency of these carbonates to decompose at potentials well below the thermodynamic threshold required for reversible reactions of high-voltage systems (>4.4?V), releasing CO₂. In this work, we explore a carbonate-free electrolyte system based on a single sulfone solvent, in which a newly discovered synergy between solvent and salt simultaneously addresses the interfacial requirements of both graphitic anode and high-voltage cathode (LiNi_0.5Mn_1.5O₄ (LNMO)). Experimental measurements, quantum chemistry (QC) calculations, and molecular dynamics simulations reveal the system’s fast ion conduction, stability over a wide temperature range, and non-flammability. At the anode, a LiF-rich interphase generated by early-onset reduction of the salt anion effectively suppresses solvent co-intercalation and subsequent graphite exfoliation, enabling unprecedented and highly reversible graphite cycling in a pure sulfone system. Under oxidative conditions, QC calculations predict that high salt concentration promotes complex/aggregate formation which slow the decomposition of sulfolane and leads to polymerizable rather than gaseous products—a fundamental improvement over carbonate solvents. These predictions are corroborated by X-ray photoelectron spectroscopy (XPS), cryogenic-transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS) experiments, which revealed the presence of a thin, conformal, sulfur-based cathode electrolyte interphase (CEI). Together, the functional interphases (SEI/CEI) generated by this electrolyte system supported long term operation of a high-voltage (4.85?V) LNMO/graphite full cell, which retained ～70% of its original first-cycle discharge capacity after the 1000th cycle. Based on these results, this new carbonate-free electrolyte system, supported by the mechanistic understanding of its behavior, presents a promising new direction toward unlocking the potential of next generation Li-ion battery electrodes.     

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium‐Ion Batteries

Potassium‐ion batteries (PIBs) are attractive for low‐cost and large‐scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K⁺ ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate‐concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire‐retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity retention over 24 months of cycling (over 2000 cycles) at the 0.2 C current rate. Electrolyte structure and surface analyses show that this excellent cycling stability is due to the nearly 100% solvation of TMP molecules with K⁺ cations and the formation of FSI^?‐derived F‐rich solid electrolyte interphase (SEI), which effectively suppresses the decomposition of the solvent molecules toward the graphite anode. Furthermore, excellent performance on high‐mass loaded graphite electrodes and in a full cell with perylenetetracarboxylic dianhydride cathode is demonstrated. This study highlights the importance of the compatibility of both electrolyte and the interface, and offers new opportunities to design the electrolyte–SEI nexus for safe and practical PIBs.     

Bubble‐Sheet‐Like Interface Design with an Ultrastable Solid Electrolyte Layer for High‐Performance Dual‐Ion Batteries

In this work, a bubble‐sheet‐like hollow interface design on Al foil anode to improve the cycling stability and rate performance of aluminum anode based dual‐ion battery is reported, in which, a carbon‐coated hollow aluminum anode is used as both anode materials and current collector. This anode structure can guide the alloying position inside the hollow nanospheres, and also confine the alloy sizes within the hollow nanospheres, resulting in significantly restricted volumetric expansion and ultrastable solid electrolyte interface (SEI). As a result, the battery demonstrates an excellent long‐term cycling stability within 1500 cycles with ≈99% capacity retention at 2 C. Moreover, this cell displays an energy density of 169 Wh kg^?1 even at high power density of 2113 W kg^?1 (10 C, charge and discharge within 6 min), which is much higher than most of conventional lithium ion batteries. The interfacial engineering strategy shown in this work to stabilize SEI layer and control the alloy forming position could be generalized to promote the research development of metal anodes based battery systems.     

A Novel Graphite–Graphite Dual Ion Battery Using an AlCl3–[EMIm]Cl Liquid Electrolyte

Herein, a novel graphite–graphite dual ion battery (GGDIB) based on a AlCl₃/1‐ethyl‐3‐methylimidazole Cl ([EMIm]Cl) room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated, that is, metallic aluminum is deposited/dissolved on the surface of the anode, and chloroaluminate ions are intercalated/deintercalated in the cathode material. The self‐discharge phenomenon and pseudocapacitive behavior of the GGDIB are also analyzed. The GGDIB shows excellent rate performance and cycle performance due to the high ionic conductivity of ionic liquids. The initial discharge capacity is 76.5 mA h g⁻¹ at a current density of 200 mA g⁻¹ over a voltage window of 0.1–2.3 V, and the capacity remains at 62.3 mA h g⁻¹ after 1000 cycles with a corresponding capacity retention of 98.42% at a current density of 500 mA g⁻¹. With the merits of environmental friendliness and low cost, the GGDIB has a great advantage in the future of energy storage application.     

A Molecularly Engineered Cathode Lithium Compensation Agent for High Energy Density Batteries

Prelithiating cathode is considered as one of the most promising lithium compensation strategies for practical high energy density batteries. Whereas most of reported cathode lithium compensation agents are deficient owing to their poor air-stability, residual insulating solid, or formidable Li-extracting barrier. Here, this work proposes molecularly engineered 4-Fluoro-1,2-dihydroxybenzene Li salt (LiDF) with high specific capacity (382.7 mAh g⁻¹) and appropriate delithiation potential (3.6–4.2 V) as an air-stable cathode Li compensation agent. More importantly, the charged residue 4-Fluoro-1,2-benzoquinone (BQF) can synergistically work as an electrode/electrolyte interface forming additive to build uniform and robust LiF-riched cathode/anode electrolyte interfaces (CEI/SEI). Consequently, less Li loss and retrained electrolyte decomposition are achieved. With 2 wt% 4-Fluoro-1,2-dihydroxybenzene Li salt initially blended within the cathode, 1.3 Ah pouch cells with NCM (Ni92) cathode and SiO/C (550 mAh g⁻¹) anode can keep 91% capacity retention after 350 cycles at 1 C rate. Moreover, the anode free of NCM622+LiDF||Cu cell achieves 78% capacity retention after 100 cycles with the addition of 15 wt% LiDF. This work provides a feasible sight for the rational designing Li compensation agent at molecular level to realize high energy density batteries.     

Ionic conductive polymers as artificial solid electrolyte interphase films in Li metal batteries – A review

Lithium (Li) metal has been considered as the ultimate anode material for next-generation rechargeable batteries due to its ultra-high theoretical specific capacity (3860 mAh g⁻¹) and the lowest reduction voltage (−3.04 V vs the standard hydrogen electrode). However, the dendritic Li formation, uncontrolled interfacial reactions, and huge volume variations lead to unstable solid electrolyte interphase (SEI) layer, low Coulombic efficiency and hence short cycling lifetime. Designing artificial solid electrolyte interphase (artificial SEI) films on the Li metal electrode exhibits great potential to solve the aforementioned problems and enable Li–metal batteries with prolonged lifetime. Polymer materials with good ionic conductivity, superior processability and high flexibility are considered as ideal artificial SEI film materials. In this review, according to the ionic conductive groups, recent advances in polymeric artificial SEI films are summarized to afford a deep understanding of Li ion plating/stripping behavior and present design principles of high-performance artificial SEI films in achieving stable Li metal electrodes. Perspectives regarding to the future research directions of polymeric artificial SEI films for Li–metal electrode are also discussed. The insights and design principles of polymeric artificial SEI films gained in the current review will be definitely useful in achieving the Li–metal batteries with improved energy density, high safety and long cycling lifetime toward next-generation energy storage devices.     

A Liquid‐Metal‐Enabled Versatile Organic Alkali‐Ion Battery

Despite the high specific capacity and low redox potential of alkali metals, their practical application as anodes is still limited by the inherent dendrite‐growth problem. The fusible sodium–potassium (Na–K) liquid metal alloy is an alternative that detours this drawback, but the fundamental understanding of charge transport in this binary electroactive alloy anode remains elusive. Here, comprehensive characterization, accompanied with density function theory (DFT) calculations, jointly expound the Na–K anode‐based battery working mechanism. With the organic cathode sodium rhodizonate dibasic (SR) that has negligible selectivity toward cations, the charge carrier is screened by electrolytes due to the selective ionic pathways in the solid electrolyte interphase (SEI). Stable cycling for this Na–K/SR battery is achieved with capacity retention per cycle to be 99.88% as a sodium‐ion battery (SIB) and 99.70% as a potassium‐ion battery (PIB) for over 100 cycles. Benefitting from the flexibility of the liquid metal and the specially designed carbon nanofiber (CNF)/SR layer‐by‐layer cathode, a flexible dendrite‐free alkali‐ion battery is achieved with an ultrahigh areal capacity of 2.1 mAh cm^?2. Computation‐guided materials selection, characterization‐supported mechanistic understanding, and self‐validating battery performance collectively promise the prospect of a high‐performance, dendrite‐free, and versatile organic‐based liquid metal battery.     

LiNi0.8Co0.15Al0.05O2/石墨锂离子电池高荷电存储老化机理研究

高荷电存储寿命对锂离子电池的使用性能具有重要影响, 但是相关研究却较为缺乏。本研究通过高温加速实验, 研究了LiNi_0.8Co_0.15Al_0.05O₂(NCA)/石墨锂离子电池在55 ℃下的存储寿命, 分析了正负极材料在电池寿命终点时的电化学性能和界面变化。研究结果表明, 在55 ℃、高荷电状态下NCA/石墨锂离子电池的存储寿命约为90 d。在寿命终点时, 正负极活性材料的容量有一定下降, 但不是电池容量衰减的主要原因。界面分析表明, 存储后负极表面固体电解质界面(SEI)膜增长明显, 而正极表面固体电解质界面(PEI)膜无明显变化。SEI膜的增长主要是由于电解液溶剂和锂反应, 造成石墨内锂损失, 使电池内可循环锂减少, 这是NCA/石墨电池在存储过程中容量损失的主要原因。     

Review of Recent Development of In Situ/Operando Characterization Techniques for Lithium Battery Research

The increasing demands of energy storage require the significant improvement of current Li‐ion battery electrode materials and the development of advanced electrode materials. Thus, it is necessary to gain an in‐depth understanding of the reaction processes, degradation mechanism, and thermal decomposition mechanisms under realistic operation conditions. This understanding can be obtained by in situ/operando characterization techniques, which provide information on the structure evolution, redox mechanism, solid‐electrolyte interphase (SEI) formation, side reactions, and Li‐ion transport properties under operating conditions. Here, the recent developments in the in situ/operando techniques employed for the investigation of the structural stability, dynamic properties, chemical environment changes, and morphological evolution are described and summarized. The experimental approaches reviewed here include X‐ray, electron, neutron, optical, and scanning probes. The experimental methods and operating principles, especially the in situ cell designs, are described in detail. Representative studies of the in situ/operando techniques are summarized, and finally the major current challenges and future opportunities are discussed. Several important battery challenges are likely to benefit from these in situ/operando techniques, including the inhomogeneous reactions of high‐energy‐density cathodes, the development of safe and reversible Li metal plating, and the development of stable SEI.     

Beyond Activated Carbon: Graphite‐Cathode‐Derived Li‐Ion Pseudocapacitors with High Energy and High Power Densities

Supercapacitors have aroused considerable attention due to their high power capability, which enables charge storage/output in minutes or even seconds. However, to achieve a high energy density in a supercapacitor has been a long‐standing challenge. Here, graphite is reported as a high‐energy alternative to the frequently used activated carbon (AC) cathode for supercapacitor application due to its unique Faradaic pseudocapacitive anion intercalation behavior. The graphite cathode manifests both higher gravimetric and volumetric energy density (498 Wh kg^?1 and 431.2 Wh l^?1) than an AC cathode (234 Wh kg^?1 and 83.5 Wh l^?1) with peak power densities of 43.6 kW kg^?1 and 37.75 kW l^?1. A new type of Li‐ion pseudocapacitor (LIpC) is thus proposed and demonstrated with graphite as cathode and prelithiated graphite or Li₄Ti₅O₁₂ (LTO) as anode. The resultant graphite–graphite LIpCs deliver high energy densities of 167–233 Wh kg^?1 at power densities of 0.22–21.0 kW kg^?1 (based on active mass in both electrodes), much higher than 20–146 Wh kg^?1 of AC‐derived Li‐ion capacitors and 23–67 Wh kg^?1 of state‐of‐the‐art metal oxide pseudocapacitors. Excellent rate capability and cycling stability are further demonstrated for LTO‐graphite LIpCs.     

High‐Capacity Cathode Material with High Voltage for Li‐Ion Batteries

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high‐capacity electrode materials. According to the concept of energy quality, a high‐voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high‐capacity Li‐rich cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after‐treatment, and the specific energy is improved from 912 to 1033 Wh kg^?1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.     

A High Energy and Power Li‐Ion Capacitor Based on a TiO2 Nanobelt Array Anode and a Graphene Hydrogel Cathode

A novel hybrid Li‐ion capacitor (LIC) with high energy and power densities is constructed by combining an electrochemical double layer capacitor type cathode (graphene hydrogels) with a Li‐ion battery type anode (TiO₂ nanobelt arrays). The high power source is provided by the graphene hydrogel cathode, which has a 3D porous network structure and high electrical conductivity, and the counter anode is made of free‐standing TiO₂ nanobelt arrays (NBA) grown directly on Ti foil without any ancillary materials. Such a subtle designed hybrid Li‐ion capacitor allows rapid electron and ion transport in the non‐aqueous electrolyte. Within a voltage range of 0.0?3.8 V, a high energy of 82 Wh kg^?1 is achieved at a power density of 570 W kg^?1. Even at an 8.4 s charge/discharge rate, an energy density as high as 21 Wh kg^?1 can be retained. These results demonstrate that the TiO₂ NBA//graphene hydrogel LIC exhibits higher energy density than supercapacitors and better power density than Li‐ion batteries, which makes it a promising electrochemical power source.     

Dual‐Functionalized Double Carbon Shells Coated Silicon Nanoparticles for High Performance Lithium‐Ion Batteries

To address the challenge of huge volume change and unstable solid electrolyte interface (SEI) of silicon in cycles, causing severe pulverization, this paper proposes a “double‐shell” concept. This concept is designed to perform dual functions on encapsulating volume change of silicon and stabilizing SEI layer in cycles using double carbon shells. Double carbon shells coated Si nanoparticles (DCS‐Si) are prepared. Inner carbon shell provides finite inner voids to allow large volume changes of Si nanoparticles inside of inner carbon shell, while static outer shell facilitates the formation of stable SEI. Most importantly, intershell spaces are preserved to buffer volume changes and alleviate mechanical stress from inner carbon shell. DCS‐Si electrodes display a high rechargeable specific capacity of 1802 mAh g⁻¹ at a current rate of 0.2 C, superior rate capability and good cycling performance up to 1000 cycles. A full cell of DCS‐Si//LiNi_0.45Co_0.1Mn_1.45O₄ exhibits an average discharge voltage of 4.2 V, a high energy density of 473.6 Wh kg⁻¹, and good cycling performance. Such double‐shell concept can be applied to synthesize other electrode materials with large volume changes in cycles by simultaneously enhancing electronic conductivity and controlling SEI growth.