Biomass-Derived Materials for Advanced Rechargeable Batteries.

Biomass-derived materials generally exhibit uniform and highly-stable hierarchical porous structures that can hardly be achieved by conventional chemical synthesis and artificial design. When used as electrodes for rechargeable batteries, these structural and compositional advantages often endow the batteries with superior electrochemical performances. This review systematically introduces the innate merits of biomass-derived materials and their applications as the electrode for advanced rechargeable batteries, including lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, and metal-sulfur batteries. In addition, biomass-derived materials as catalyst supports for metal-air batteries, fuel cells, and redox-flow batteries are also included. The major challenges for specific batteries and the strategies for utilizing biomass-derived materials are detailly introduced. Finally, the future development of biomass-derived materials for advanced rechargeable batteries is prospected. This review aims to promote the development of biomass-derived materials in the field of energy storage and provides effective suggestions for building advanced rechargeable batteries.

Understanding the Coupling Mechanism of Intercalation and Conversion Hybrid Storage in Lithium-Graphite Anode.

Anodes with high capacity and long lifespan play an important role in the advanced batteries. However, none of the existing anodes can meet these two requirements simultaneously. Lithium (Li)-graphite composite anode presents great potential in balancing these two requirements. Herein, the working mechanism of Li-graphite composite anode is comprehensively investigated. The capacity decay features of the composite anode are different from those of Li ion intercalation in Li ion batteries and Li metal deposition in Li metal batteries. An intercalation and conversion hybrid storage mechanism are proposed by analyzing the capacity decay ratios in the composite anode with different initial specific capacities. The capacity decay models can be divided into four stages including Capacity Retention Stage, Relatively Independent Operation Stage, Intercalation & Conversion Coupling Stage, Pure Li Intercalation Stage. When the specific capacity is between 340 and 450 mAh g-1, its capacity decay ratio is between that of pure intercalation and conversion model. These results intensify the comprehensive understandings on the working principles in Li-graphite composite anode and present novel insights in the design of high-capacity and long-lifespan anode materials for the next-generation batteries.

Electrochemically and Thermally Stable Inorganics-Rich Solid Electrolyte Interphase for Robust Lithium Metal Batteries.

Severe dendrite growth and high-level activity of the lithium metal anode lead to a short life span and poor safety, seriously hindering the practical applications of lithium metal batteries. With a trisalt electrolyte design, an F-/N-containing inorganics-rich solid electrolyte interphase on a lithium anode is constructed, which is electrochemically and thermally stable over long-term cycles and safety abuse conditions. As a result, its Coulombic efficiency can be maintained over 98.98% for 400 cycles. An 85.0% capacity can be retained for coin-type full cells with a 3.14 mAh cm-2 LiNi0.5 Co0.2 Mn0.3 O2 cathode after 200 cycles and 1.0 Ah pouch-type full cells with a 4.0 mAh cm-2 cathode after 72 cycles. During the thermal runaway tests of a cycled 1.0 Ah pouch cell, the onset and triggering temperatures were increased from 70.8 °C and 117.4 °C to 100.6 °C and 153.1 °C, respectively, indicating a greatly enhanced safety performance. This work gives novel insights into electrolyte and interface design, potentially paving the way for high-energy-density, long-life-span, and thermally safe lithium metal batteries.

Synchronization of parallel intense electron beam accelerators based on single trigger generator.

In this study, the authors provide results of the precisely synchronized triggering of an intense electron beam accelerator (IEBA). The trigger generator was composed of a fractional-turn ratio saturable-pulse transformer and a compact six-stage Marx generator. The main switch of the IEBA was a corona-stabilized triggered switch (CSTS) based on the stabilized corona mechanism. The output voltage of a single IEBA exceeded 500 kV with less than 4 ns of jitter on a 50 Ω dummy load. We also conducted an experiment on the synchronous triggering of two IEBAs by using two independent trigger generators. The synchronization-related jitter was 6.1 ns, while the average time difference was 1.3 ns. We used this to attempt to trigger two parallel IEBAs by using a single trigger generator. The results showed a reduction in the synchronization-related jitter of 31% to 4.2 ns. The designs of the CSTS and the trigger generator guaranteed a precisely synchronous trigger by using a single trigger generator. Thus, the proposed method appears to be promising for accurately and synchronously triggering multiple IEBAs by using a single trigger generator. This provides an effective method to generate pulses with high power.

Heterostructures Regulating Lithium Polysulfides for Advanced Lithium-Sulfur Batteries.

Sluggish reaction kinetics and severe shuttling effect of lithium polysulfides seriously hinder the development of lithium-sulfur batteries. Heterostructures, due to unique properties, have congenital advantages that are difficult to be achieved by single-component materials in regulating lithium polysulfides by efficient catalysis and strong adsorption to solve the problems of poor reaction kinetics and serious shuttling effect of lithium-sulfur batteries. In this review, the principles of heterostructures expediting lithium polysulfides conversion and anchoring lithium polysulfides are detailedly analyzed, and the application of heterostructures as sulfur host, interlayer, and separator modifier to improve the performance of lithium-sulfur batteries is systematically reviewed. Finally, the problems that need to be solved in the future study and application of heterostructures in lithium-sulfur batteries are prospected. This review will provide a valuable reference for the development of heterostructures in advanced lithium-sulfur batteries.

Thermoresponsive Electrolytes for Safe Lithium-Metal Batteries.

Exploring advanced strategies in alleviating the thermal runaway of lithium-metal batteries (LMBs) is critically essential. Herein, a novel electrolyte system with thermoresponsive characteristics is designed to largely enhance the thermal safety of 1.0 Ah LMBs. Specifically, vinyl carbonate (VC) with azodiisobutyronitrile is introduced as a thermoresponsive solvent to boost the thermal stability of both the solid electrolyte interphase (SEI) and electrolyte. First, abundant poly(VC) is formed in SEI with thermoresponsive electrolyte, which is more thermally stable against lithium hexafluorophosphate compared to the inorganic components widely acquired in routine electrolyte. This increases the critical temperature for thermal safety (the beginning temperature of obvious self-heating) from 71.5 to 137.4 °C. The remained VC solvents can be polymerized into poly(VC) as the battery temperature abnormally increases. The poly(VC) can not only afford as a barrier to prevent the direct contact between electrodes, but also immobilize the free liquid solvents, thereby reducing the exothermic reactions between electrodes and electrolytes. Consequently, the internal-short-circuit temperature and "ignition point" temperature (the starting temperature of thermal runaway) of LMBs are largely increased from 126.3 and 100.3 °C to 176.5 and 203.6 °C. This work provides novel insights for pursuing thermally stable LMBs with the addition of various thermoresponsive solvents in commercial electrolytes.

Thermally Stable Polymer-Rich Solid Electrolyte Interphase for Safe Lithium Metal Pouch Cells.

Serious safety risks caused by the high reactivity of lithium metal against electrolytes severely hamper the practicability of lithium metal batteries. By introducing unique polymerization site and more fluoride substitution, we built an in situ formed polymer-rich solid electrolyte interphase upon lithium anode to improve battery safety. The fluorine-rich and hydrogen-free polymer exhibits high thermal stability, which effectively reduces the continuous exothermic reaction between electrolyte and anode/cathode. As a result, the critical temperature for thermal safety of 1.0 Ah lithium-LiNi0.5 Co0.2 Mn0.3 O2 pouch cell can be increased from 143.2 °C to 174.2 °C. The more dangerous "ignition" point of lithium metal batteries, the starting temperature of battery thermal runaway, has been dramatically raised from 240.0 °C to 338.0 °C. This work affords novel strategies upon electrolyte design, aiming to pave the way for high-energy-density and thermally safe lithium metal batteries.

A compact, low jitter, high voltage trigger generator based on fractional-turn ratio saturable pulse transformer and its application.

In this paper, an all-solid-state high voltage trigger generator is developed, which is aimed at triggering a several gigawatts three-electrode spark gap of an intense electron beam accelerator (IEBA). As one of the most important parts for triggering the IEBA precisely, it is developed based on a fractional-turn ratio saturable pulse transformer and a compact six-stage Marx generator. A pulse of rising time 141 ns and amplitude 79.6 kV is obtained on the 1000 Ω dummy load. The trigger is operated at pulsed repetition frequency over 10 Hz for testing its operational stability. The jitter counted from the initial control signal to the falling edge of the pulse is 0.64 ns. In addition, experiments of three-minute continuous repetitive operations at 10 Hz and higher frequency are carried out. The results show that the trigger generator has high stability even in long-time operations. So far, it successfully applies to the main switch of IEBA with a breakdown voltage of over 500 kV, and a total system jitter of 6.7 ns is acquired.

Nickel-iron nanoparticles encapsulated in carbon nanotubes prepared from waste plastics for low-temperature solid oxide fuel cells.

Low-temperature solid oxide fuel cells (LT-SOFCs) are a promising next-generation fuel cell due to their low cost and rapid start-up, posing a significant challenge to electrode materials with high electrocatalytic activity. Herein, we reported the bimetallic nanoparticles encapsulated in carbon nanotubes (NiFe@CNTs) prepared by carefully controlling catalytic pyrolysis of waste plastics. Results showed that plenty of multi-walled CNTs with outer diameters (14.38 ± 3.84 nm) were observed due to the smallest crystalline size of Ni-Fe alloy nanoparticles. SOFCs with such NiFe@CNTs blended in anode exhibited remarkable performances, reaching a maximum power density of 885 mW cm-2 at 500°C. This could be attributed to the well-dispersed alloy nanoparticles and high graphitization degree of NiFe@CNTs to improve HOR activity. Our strategy could upcycle waste plastics to produce nanocomposites and demonstrate a high-performance LT-SOFCs system, addressing the challenges of sustainable waste management and guaranteeing global energy safety simultaneously.

A Diffusion--Reaction Competition Mechanism to Tailor Lithium Deposition for Lithium-Metal Batteries.

Lithium metal is recognized as one of the most promising anode materials owing to its ultrahigh theoretical specific capacity and low electrochemical potential. Nonetheless, dendritic Li growth has dramatically hindered the practical applications of Li metal anodes. Realizing spherical Li deposition is an effective approach to avoid Li dendrite growth, but the mechanism of spherical deposition is unknown. Herein, a diffusion-reaction competition mechanism is proposed to reveal the rationale of different Li deposition morphologies. By controlling the rate-determining step (diffusion or reaction) of Li deposition, various Li deposition scenarios are realized, in which the diffusion-controlled process tends to lead to dendritic Li deposition while the reaction-controlled process leads to spherical Li deposition. This study sheds fresh light on the dendrite-free Li metal anode and guides to achieve safe batteries to benefit future wireless and fossil-fuel-free world.

Three-Dimensional Superlithiophilic Interphase for Dendrite-Free Lithium Metal Anodes.

Lithium metal is among the most promising anode candidates of high-energy-density batteries. However, the formed dendrites result in low Coulombic efficiency and serious security issues. Designing lithiophilic sites is one of the effective strategies to control Li deposition. Herein, we propose a three-dimensional lithiophilic N-rich carbon nanofiber with the decoration of ZnO granules as a protective layer for a dendrite-free lithium metal anode. Theoretical evaluation indicates the synergistic effects of lithiophilic ZnO and N-containing functional groups enhance lithium adsorption and trigger uniform deposition. With the lithiophilic interlayer, the lithium deposition overpotential is only ∼20, 50, and 74 mV at 1, 3, and 6 mA cm-2, respectively, which are much lower than those without the functional interlayer (∼55, 130, and 238 mV). The average Coulombic efficiency of lithium stripping and plating is up to ∼97.4% (94.0% for that without the interlayer) at 0.5 mA cm-2. Meanwhile, the Li|LiFePO4 full cell with the superlithiophilic interlayer demonstrates a high capacity retention rate of 99.6% (91.0% for that without the interlayer) over 200 cycles at 1 C. The introduction of the lithiophilic interphase could provide a convenient strategy and guidance to design the configuration for the practical application of Li metal batteries.

Favorable Lithium Nucleation on Lithiophilic Framework Porphyrin for Dendrite-Free Lithium Metal Anodes.

Lithium metal constitutes promising anode materials but suffers from dendrite growth. Lithiophilic host materials are highly considered for achieving uniform lithium deposition. Precise construction of lithiophilic sites with desired structure and homogeneous distribution significantly promotes the lithiophilicity of lithium hosts but remains a great challenge. In this contribution, a framework porphyrin (POF) material with precisely constructed lithiophilic sites in regard to chemical structure and geometric position is employed as the lithium host to address the above issues for dendrite-free lithium metal anodes. The extraordinary lithiophilicity of POF even beyond lithium nuclei validated by DFT simulations and lithium nucleation overpotentials affords a novel mechanism of favorable lithium nucleation to facilitate uniform nucleation and inhibit dendrite growth. Consequently, POF-based anodes demonstrate superior electrochemical performances with high Coulombic efficiency over 98%, reduced average voltage hysteresis, and excellent stability for 300 cycles at 1.0 mA cm-2, 1.0 mAh cm-2 superior to both Cu and graphene anodes. The favorable lithium nucleation mechanism on POF materials inspires further investigation of lithiophilic electrochemistry and development of lithium metal batteries.

Electrochemical Diagram of an Ultrathin Lithium Metal Anode in Pouch Cells.

Lithium (Li) metal is regarded as a "Holy Grail" electrode for next-generation high-energy-density batteries. However, the electrochemical behavior of the Li anode under a practical working state is poorly understood, leading to a gap in the design strategy and the aim of efficient Li anodes. The electrochemical diagram to reveal failure mechanisms of ultrathin Li in pouch cells is demonstrated. The working mode of the Li metal anode ranging from 1.0 mA cm-2 /1.0 mAh cm-2 (28.0 mA/28.0 mAh) to 10.0 mA cm-2 /10.0 mAh cm-2 (280.0 mA/280.0 mAh) is investigated and divided into three categories: polarization, transition, and short-circuit zones. Powdering and the induced polarization are the main reasons for the failure of the Li electrode at small current density and capacity, while short-circuit occurs with the damage of the separator leading to safety concerns being dominant at large current and capacity. The electrochemical diagram is attributed from the distinctive plating/stripping behaviors of Li metal, accompanied by dendrites thickening and/or lengthening, and heterogeneous distribution of dendrites. A clear understanding in the electrochemical diagram of ultrathin Li is the primary step to rationally design an effective Li electrode and render a Li metal battery with high energy density, long lifespan, and enhanced safety.

Regulating the Inner Helmholtz Plane for Stable Solid Electrolyte Interphase on Lithium Metal Anodes.

The stability of a battery is strongly dependent on the feature of solid electrolyte interphase (SEI). The electrical double layer forms prior to the formation of SEI at the interface between the Li metal anode and the electrolyte. The fundamental understanding on the regulation of the SEI structure and stability on Li surface through the structure of the electrical double layer is highly necessary for safe batteries. Herein, the interfacial chemistry of the SEI is correlated with the initial Li surface adsorption electrical double layer at the nanoscale through theoretical and experimental analysis. Under the premise of the constant solvation sheath structure of Li+ in bulk electrolyte, a trace amount of lithium nitrate (LiNO3) and copper fluoride (CuF2) were employed in electrolytes to build robust electric double layer structures on a Li metal surface. The distinct results were achieved with the initial competitive adsorption of bis(fluorosulfonyl)imide ion (FSI-), fluoride ion (F-), and nitrate ion (NO3-) in the inner Helmholtz plane. As a result, Cu-NO3- complexes are preferentially adsorbed and reduced to form the SEI. The modified Li metal electrode can achieve an average Coulombic efficiency of 99.5% over 500 cycles, enabling a long lifespan and high capacity retention of practical rechargeable batteries. The as-proposed mechanism bridges the gap between Li+ solvation and the adsorption about the electrode interface formation in a working battery.

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.

Lithiophilicity chemistry of heteroatom-doped carbon to guide uniform lithium nucleation in lithium metal anodes.

The uncontrollable growth of lithium (Li) dendrites seriously impedes practical applications of Li metal batteries. Various lithiophilic conductive frameworks, especially carbon hosts, are used to guide uniform Li nucleation and thus deliver a dendrite-free composite anode. However, the lithiophilic nature of these carbon hosts is poorly understood. Herein, the lithiophilicity chemistry of heteroatom-doped carbon is investigated through both first principles calculations and experimental verifications to guide uniform Li nucleation. The electronegativity, local dipole, and charge transfer are proposed to reveal the lithiophilicity of doping sites. Li bond chemistry further deepens the understanding of lithiophilicity. The O-doped and O/B-co-doped carbons exhibit the best lithiophilicity among single-doped and co-doped carbons, respectively. The excellent lithiophilicity achieved by O-doping carbon is further validated by Li nucleation overpotential measurement. This work uncovers the lithiophilicity chemistry of heteroatom-doped carbons and affords a mechanistic guidance to Li metal anode frameworks for safe rechargeable batteries.

Lithiophilic LiC6 Layers on Carbon Hosts Enabling Stable Li Metal Anode in Working Batteries.

Lithium (Li) metal-based battery is among the most promising candidates for next-generation rechargeable high-energy-density batteries. Carbon materials are strongly considered as the host of Li metal to relieve the powdery/dendritic Li formation and large volume change during repeated cycles. Herein, we describe the formation of a thin lithiophilic LiC6 layer between carbon fibers (CFs) and metallic Li in Li/CF composite anode obtained through a one-step rolling method. An electron deviation from Li to carbon elevates the negativity of carbon atoms after Li intercalation as LiC6 , which renders stronger binding between carbon framework and Li ions. The Li/CF | Li/CF batteries can operate for more than 90 h with a small polarization voltage of 120 mV at 50% discharge depth. The Li/CF | sulfur pouch cell exhibits a high discharge capacity of 3.25 mAh cm-2 and a large capacity retention rate of 98% after 100 cycles at 0.1 C. It is demonstrated that the as-obtained Li/CF composite anode with lithiophilic LiC6 layers can effectively alleviate volume expansion and hinder dendritic and powdery morphology of Li deposits. This work sheds fresh light on the role of interfacial layers between host structure and Li metal in composite anode for long-lifespan working batteries.

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.

An Armored Mixed Conductor Interphase on a Dendrite-Free Lithium-Metal Anode.

Lithium-metal electrodes have undergone a comprehensive renaissance to meet the requirements of high-energy-density batteries due to their lowest electrode potential and the very high theoretical capacity. Unfortunately, the unstable interface between lithium and nonaqueous electrolyte induces dendritic Li and low Coulombic efficiency during repeated Li plating/stripping, which is one of the huge obstacles toward practical lithium-metal batteries. Here, a composite mixed ionic/electronic conductor interphase (MCI) is formed on the surface of Li by in situ chemical reactions of a copper-fluoride-based solution and Li metal at room temperature. The as-obtained MCI film acts like the armor of a soldier to protect the Li-metal anode by its prioritized lithium storage, high ionic conductivity, and high Young's modulus. The armored MCI can effectively suppress Li-dendrite growth and work effectively in LiNi0.5 Co0.2 Mn0.3 O2 /Li cells. The armored MCI presents fresh insights into the formation and regulation of the stable electrode-electrolyte interface and an effective strategy to protect Li-metal anodes in working Li-metal batteries.

Lithium Nitrate Solvation Chemistry in Carbonate Electrolyte Sustains High-Voltage Lithium Metal Batteries.

The lithium metal anode is regarded as a promising candidate in next-generation energy storage devices. Lithium nitrate (LiNO3 ) is widely applied as an effective additive in ether electrolyte to increase the interfacial stability in batteries containing lithium metal anodes. However, because of its poor solubility LiNO3 is rarely utilized in the high-voltage window provided by carbonate electrolyte. Dissolution of LiNO3 in carbonate electrolyte is realized through an effective solvation regulation strategy. LiNO3 can be directly dissolved in an ethylene carbonate/diethyl carbonate electrolyte mixture by adding trace amounts of copper fluoride as a dissolution promoter. LiNO3 protects the Li metal anode in a working high-voltage Li metal battery. When a LiNi0.80 Co0.15 Al0.05 O2 cathode is paired with a Li metal anode, an extraordinary capacity retention of 53 % is achieved after 300 cycles (13 % after 200 cycles for LiNO3 -free electrolyte) and a very high average Coulombic efficiency above 99.5 % is achieved at 0.5 C. The solvation chemistry of LiNO3 -containing carbonate electrolyte may sustain high-voltage Li metal anodes operating in corrosive carbonate electrolytes.