Protection of Li metal anode by surface-coating of PVDF thin film to enhance the cycling performance of Li batteries

The PVDF thin film on the surface of the lithium metal can highly suppress the lithium dendrites.     

Characterization of SEI layer formed on high performance Si–Cu anode in ionic liquid battery electrolyte

Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of > 1620 mAhg^? 1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries.     

“Soft” graphene oxide-organopolysulfide nanocomposites for superior pseudocapacitive lithium storage

We report a "soft" graphene oxide-organopolysulfide nanocomposite with improved pseudocapacitive performance for high-potential (1-2.8 V vs. Li⁰/Li⁺), high-capacity (278 mAh/g) and stable (500 cycles) lithium storage.     

Catalytic Chemistry Derived Artificial Solid Electrolyte Interphase for Stable Lithium Metal Anodes Working at 20 mA cm−2 and 20 mAh cm−2

A stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long-term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst-derived artificial SEI layer with an ordered polyamide-lithium hydroxide (PA-LiOH) bi-phase structure to modulate ion transport and enable dendrite-free Li deposition. The PA-LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra-high current density of 20 mA cm⁻² in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive-free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm⁻² with a capacity of 1 mAh cm⁻².     

A Chemically Bonded Ultraconformal Layer between the Elastic Solid Electrolyte and Lithium Anode for High-performance Lithium Metal Batteries

Although high ionic conductivities have been achieved in most solid-state electrolytes used in lithium metal batteries (LMBs), rapid and stable lithium-ion transport between solid-state electrolytes and lithium anodes remains a great challenge due to the high interfacial impedances and infinite volume changes of metallic lithium. In this work, a chemical vapor-phase fluorination approach is developed to establish a lithiophilic surface on rubber-derived electrolytes, which results in the formation of a resilient, ultrathin, and mechanically integral LiF-rich layer after electrochemical cycling. The resulting ultraconformal layer chemically connects the electrolyte and lithium anode and maintains dynamic contact during operation, thus facilitating rapid and stable lithium-ion transport across interfaces, as well as promoting uniform lithium deposition and inhibiting side reactions between electrolyte components and metallic lithium. LMBs containing the novel electrolyte have an ultralong cycling life of 2500 h and deliver a high critical current density of 1.1 mA cm⁻² in lithium symmetric cells as well as showing good stability over 300 cycles in a full cell.     

Locally Concentrated Ionic Liquid Electrolytes Enabling Low-Temperature Lithium Metal Batteries

Lithium metal is a promising anode material for next-generation high-energy-density batteries but suffers from low stripping/plating Coulombic efficiency and dendritic growth particularly at sub-zero temperatures. Herein, a poorly-flammable, locally concentrated ionic liquid electrolyte with a wide liquidus range extending well below 0 °C is proposed for low-temperature lithium metal batteries. Its all-anion Li⁺ solvation and phase-nano-segregation solution structure are sustained at low temperatures, which, together with a solid electrolyte interphase rich in inorganic compounds, enable dendrite-free operation of lithium metal anodes at −20 °C and 0.5 mA cm⁻², with a Coulombic efficiency of 98.9 %. As a result, lithium metal batteries coupling thin lithium metal anodes (4 mAh cm⁻²) and high-loading LiNi_0.8Co_0.15Al_0.05O₂ cathodes (10 mg cm⁻²) retain 70 % of the initial capacity after 100 cycles at −20 °C. These results, as a proof of concept, demonstrate the applicability of locally concentrated ionic liquid electrolytes for low-temperature lithium metal batteries.     

Flexible Amalgam Film Enables Stable Lithium Metal Anodes with High Capacities

Dendrite formation is a critical challenge for the applications of lithium (Li) metal anodes. In this work a new strategy is demonstrated to address this issue by fabricating an Li amalgam film on its surface. This protective film serves as a flexible buffer that affords repeated Li plating/stripping. In symmetric cells, the protected Li electrodes exhibit stable cycling over 750 hours at a high plating current and capacity of 8 mA cm^?2 and 8 mAh cm^?2, respectively. Coupled with high‐loading cathodes (ca. 12 mg cm^?2) such as LiFePO₄ and LiNi_0.6Co_0.2Mn_0.2O₂, the protected hybrid anodes demonstrate significantly improved cell stability, indicating its reliability for practical development of Li metal batteries. Interfacial analyses reveal a unique plating‐alloying synergistic function of the protective film, where Li beneath the film is actively involved in the electrode reactions upon cycling. Lithium amalgams enrich the alloy anode family and provide new perspectives for the rational design of dendrite‐free anodes.     

Double‐Shelled C@MoS2 Structures Preloaded with Sulfur: An Additive Reservoir for Stable Lithium Metal Anodes

The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS₂ coated hollow carbon particles preloaded with sulfur (C@MoS₂/S), was designed to modify the LMA. The C@MoS₂ hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium‐based components. These two factors together effectively suppress the growth of Li dendrites. The as‐modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm^?2. When matched with a LiFePO₄ cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA.     

Double-Shelled C@MoS2 Structures Preloaded with Sulfur: An Additive Reservoir for Stable Lithium Metal Anodes

The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS₂ coated hollow carbon particles preloaded with sulfur (C@MoS₂/S), was designed to modify the LMA. The C@MoS₂ hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium-based components. These two factors together effectively suppress the growth of Li dendrites. The as-modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm⁻². When matched with a LiFePO₄ cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA.     

Inhibition of lithium dendrites and dead lithium by an ionic liquid additive toward safe and stable lithium metal anodes

The uncontrolled growth of lithium dendrites and accumulation of “dead lithium” upon cycling are among the main obstacles that hinder the widespread application of lithium metal anodes. Herein, an ionic liquid (IL) consisting of 1-methyl-1-propylpiperidinium cation (Pp₁₃⁺) and bis(fluorosulfonyl)imide anion (FSI^?), was chosen as the additive in propylene carbonate (PC)-based liquid electrolytes to circumvent the shortcoming of lithium metal anodes. The optimal 1% Pp₁₃FSI acts as the role of electrostatic shielding, lithiophobic effect and participating in the formation of solid electrolyte interface (SEI) layer with enhanced properties. The in-situ optical microscopy records that the addition of IL can effectively inhibit the growth of lithium dendrites and the corrosion of lithium anode. This study delivers an effective modification to optimize electrolytes for stable lithium metal batteries.     

Fabrication and properties of three-dimensional macroporous Sn–Ni alloy electrodes of high preferential (1 1 0) orientation for lithium ion batteries

One of the most important problems in utilizing Sn-based intermetallic compound anodes is its poor cyclability due to mechanical fatigue caused by volume change during lithium insertion and extraction processes. To overcome this problem, a new facile procedure to prepare three-dimensional (3D) macroporous materials of Sn–Ni alloy by using colloidal crystal template method is presented. The structural and electrochemical characteristics of 3D macroporous Sn–Ni alloy were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), galvanostatic cycling. When used as a negative electrode for a rechargeable lithium battery, the 3D macroporous Sn–Ni alloy electrode delivered a reversible capacity of 536.1 mAh g⁻¹ up to 75th cycles.     

Solvation Modulation Enhances Anion-Derived Solid Electrolyte Interphase for Deep Cycling of Aqueous Zinc Metal Batteries

Stable Zn anodes with a high utilization efficiency pose a challenge due to notorious dendrite growth and severe side reactions. Therefore, electrolyte additives are developed to address these issues. However, the additives are always consumed by the electrochemical reactions over cycling, affecting the cycling stability. Here, hexamethylphosphoric triamide (HMPA) is reported as an electrolyte additive for achieving stable cycling of Zn anodes. HMPA reshapes the solvation structures and promotes anion decomposition, leading to the in situ formation of inorganic-rich solid-electrolyte-interphase. More interestingly, this anion decomposition does not involve HMPA, preserving its long-term impact on the electrolyte. Thus, the symmetric cells with HMPA in the electrolyte survive ≈500 h at 10 mA cm⁻² for 10 mAh cm⁻² or ≈200 h at 40 mA cm⁻² for 10 mAh cm⁻² with a Zn utilization rate of 85.6 %. The full cells of Zn||V₂O₅ exhibit a record-high cumulative capacity even under a lean electrolyte condition (E/C ratio=12 μL mAh⁻¹), a limited Zn supply (N/P ratio=1.8) and a high areal capacity (6.6 mAh cm⁻²).     

Pulse polymerized polypyrrole electrodes for high energy density electrochemical supercapacitor

A novel method of pulsed polymerization for pyrrole exhibiting highest capacitance and very high energy density polypyrrole supercapacitor is reported. Stable polypyrrole films with good electrochemical reversibility and high doping degree were obtained by applying ultra short on time current pulse for polymerization. Pulse on time plays an important role in controlling chain size and chain defects whereas pulse off time contributes in polymer conjugation and orientation. A regime of pulse on time is identified to yield highly capacitive and stable films for supercapacitor application. Very high specific capacitance of 400 F/g and an unexpectedly high energy density of 250 Wh/kg were obtained form pulsed polymerized ordered polypyrrole structures in acidic electrolyte. Stability tests performed on pulsed polymerized pPy electrode yield long cycling life up to 10,000 cycles at charge/discharge current density of 5 mA/cm².     

Highly electroactive nanosized α-LiFeO2

We obtained pure nanosized α-LiFeO₂ by a simple and quick method involving the reaction between goethite, lithium hydroxide and lithium nitrate at temperatures as low as 523 K. Unlike the known limited electrochemical activity of this polymorph, cells based on our nanosized electrode provided a remarkable high capacity in the first cycles and showed a good cycling life, due to its nanosized character and adequate morphology to enhance lithium insertion/deinsertion. Capacity values when cycling in the 1.5–4.5 V range are up to 150 mAh g⁻¹ in the 50th cycle. To our knowledge, the capacity values and its retention upon cycling are the best reported for this polymorph in an un-doped state.     

Phosphatization: A promising approach to enhance the performance of mesoporous TiO2 anode for lithium ion batteries

We report phosphatization is a promising method to enhance the performance of mesoporous TiO₂ anode for lithium ion batteries. The resulting phosphated mesoporous TiO₂ possessed higher reversible capacity and better cycling stability than the pure mesoporous TiO₂. When cycled at 30 mA/g between 3.0 and 1.0 V, the initial capacity of phosphate mesoporous TiO₂ was 249 mA h/g, significantly higher than that of pure mesoporous TiO₂ (204 mA h/g). After 40 cycles, the capacity retention ratio of phosphate mesoporous TiO₂ reached 83.7%, while pure mesoporous TiO₂ had merely a capacity retention ratio of 62.3%. We believe that this phosphatization process could be used to enhance the electrochemical performance of other metal oxides for lithium ion batteries.     

Self-Stabilized and Strongly Adhesive Supramolecular Polymer Protective Layer Enables Ultrahigh-Rate and Large-Capacity Lithium-Metal Anode

Constructing a solid electrolyte interface (SEI) is a highly effective approach to overcome the poor reversibility of lithium (Li) metal anodes. Herein, an adhesive and self-healable supramolecular copolymer, comprising of pendant poly(ethylene oxide) (PEO) segments and ureido-pyrimidinone (UPy) quadruple-hydrogen-bonding moieties, is developed as a protection layer of Li anode by a simple drop-coating. The protection performance of in-situ-formed LiPEO–UPy SEI layer is significantly enhanced owing to the strong binding and improved stability arising from a spontaneous reaction between UPy groups and Li metal. An ultrathin (approximately 70 nm) LiPEO–UPy layer can contribute to stable and dendrite-free cycling at a high areal capacity of 10 mAh cm⁻² at 5 mA cm⁻² for 1000 h. This coating together with the promising electrochemical performance offers a new strategy for the development of dendrite-free metal anodes.     

Nano-LiCoO2 as cathode material of large capacity and high rate capability for aqueous rechargeable lithium batteries

Crystalline nanoparticles of LiCoO₂ are prepared by a sol–gel method at 550 °C and characterized by X-ray diffraction. Their electrochemical behaviors were characterized by cyclic voltammograms, capacity measurement and cycling performance. Results show that the reversible capacity of the nano-LiCoO₂ can be up to 143 mAh/g at 1000 mA/g and still be 133 mAh/g at 10,000 mA/g (about 70C) in 0.5 mol/l Li₂SO₄ aqueous electrolyte. In addition, their cycling behavior is also very satisfactory, no evident capacity fading during the initial 40 cycles. These data present great promise for the application of aqueous rechargeable lithium batteries.     

Binder-free porous core–shell structured Ni/NiO configuration for application of high performance lithium ion batteries

An interwoven core–shell structured Ni/NiO anode for lithium ion batteries was created by a simple oxidation of Ni foam. As-prepared configuration has a high specific discharge capacity of 701 mAh g^?1 at the 2nd cycle. Its electrochemical performance at subsequent cycles shows good energy capacity of 646 mAh g^?1 at the 65th cycle as well as good rate capability. The porous core–shell structure not only buffers the volume change during cycling but also effectively increases the contact among anode, current collector and electrolyte. The small contact resistance between NiO and Ni facilitates enhanced intrinsic kinetics from conversion reaction.     

Grain Boundary Electronic Insulation for High-Performance All-Solid-State Lithium Batteries

Sulfide electrolytes with high ionic conductivities are one of the most highly sought for all-solid-state lithium batteries (ASSLBs). However, the non-negligible electronic conductivities of sulfide electrolytes (≈10⁻⁸ S cm⁻¹) lead to electron smooth transport through the sulfide electrolyte pellets, resulting in Li dendrite directly depositing at the grain boundaries (GBs) and serious self-discharge. Here, a grain-boundary electronic insulation (GBEI) strategy is proposed to block electron transport across the GBs, enabling Li−Li symmetric cells with 30 times longer cycling life and Li−LiCoO₂ full cells with three times lower self-discharging rate than pristine sulfide electrolytes. The Li−LiCoO₂ ASSLBs deliver high capacity retention of 80 % at 650 cycles and stable cycling performance for over 2600 cycles at 0.5 mA cm⁻². The innovation of the GBEI strategy provides a new direction to pursue high-performance ASSLBs via tailoring the electronic conductivity.     

Titanium vanadium nitride electrode for micro-supercapacitors

Here we report on the synthesis of binary transition metal nitride electrodes based on titanium vanadium nitride (TiVN) thin films. These films were deposited by a method compatible with micro-electronic processes which consists of DC co-sputtering of vanadium (V) and titanium (Ti) targets. TiVN films with different Ti/V ratio were deposited. A dependence of the capacitance and the cycling stability with the Ti/V atomic ratio in the films was established. While V rich sample exhibits a Faradic behavior that limits its cycling ability despite a high areal and volumetric capacity, the addition of Ti in the film drastically improves the cycling ability with virtually no fade in capacitance after 10,000 cycles. Furthermore, a 1.1 Ti/V ratio leads to an areal capacitance up to 15 mF·cm^− 2 in 1 M KOH electrolyte solution. Such electrodes shed light on the use of binary transition metal nitrides as candidate electrodes for micro-supercapacitor.