Synergistic Dual‐Additive Electrolyte Enables Practical Lithium‐Metal Batteries

A rechargeable Li metal anode coupled with a high‐voltage cathode is a promising approach to high‐energy‐density batteries exceeding 300 Wh kg^?1. Reported here is an advanced dual‐additive electrolyte containing a unique solvation structure and it comprises a tris(pentafluorophenyl)borane additive and LiNO₃ in a carbonate‐based electrolyte. This system generates a robust outer Li₂O solid electrolyte interface and F‐ and B‐containing conformal cathode electrolyte interphase. The resulting stable ion transport kinetics enables excellent cycling of Li/LiNi_0.8Mn_0.1Co_0.1O₂ for 140 cycles with 80 % capacity retention under highly challenging conditions (≈295.1 Wh kg^?1 at cell‐level). The electrolyte also exhibits high cycling stability for a 4.6 V LiCoO₂ (160 cycles with 89.8 % capacity retention) cathode and 4.95 V LiNi_0.5Mn_1.5O₄ cathode.     

Single Lithium‐Ion Conducting Polymer Electrolytes Based on a Super‐Delocalized Polyanion

A novel single lithium‐ion (Li‐ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4‐styrenesulfonyl)(trifluoromethyl(S‐trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI^?), and high‐molecular‐weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass‐transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li‐ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li‐ion conductivity as high as 1.35×10^?4 S cm^?1 at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.     

Polymer/colloid dual-phase electrolyte membrane for rechargeable lithium batteries

In this work, a polymer/ceramic phase-separation porous membrane is first prepared from polyvinyl alcohol–polyacrylonitrile water emulsion mixed with fumed nano-SiO₂ particles by the phase inversion method. This porous membrane is then wetted by a non-aqueous Li–salt liquid electrolyte to form the polymer/colloid dual-phase electrolyte membrane. Compared to the liquid electrolyte in conventional polyolefin separator, the obtained electrolyte membrane has superior properties in high ionic conductivity (1.9 mS?cm^?1 at 30 °C), high Li⁺ transference number (0.41), high electrochemical stability (extended up to 5.0 V versus Li⁺/Li on stainless steel electrode), and good interfacial stability with lithium metal. The test cell of Li/LiCoO₂ with the electrolyte membrane as separator also shows high-rate capability and excellent cycle performance. The polymer/colloid dual-phase electrolyte membrane shows promise for application in rechargeable lithium batteries.     

Two‐Plateau Li‐Se Chemistry for High Volumetric Capacity Se Cathodes

For Li‐Se batteries, ether‐ and carbonate‐based electrolytes are commonly used. However, because of the “shuttle effect” of the highly dissoluble long‐chain lithium polyselenides (LPSes, Li₂Se_n, 4≤n≤8) in the ether electrolytes and the sluggish one‐step solid‐solid conversion between Se and Li₂Se in the carbonate electrolytes, a large amount of porous carbon (>40 wt % in the electrode) is always needed for the Se cathodes, which seriously counteracts the advantage of Se electrodes in terms of volumetric capacity. Herein an acetonitrile‐based electrolyte is introduced for the Li‐Se system, and a two‐plateau conversion mechanism is proposed. This new Li‐Se chemistry not only avoids the shuttle effect but also facilitates the conversion between Se and Li₂Se, enabling an efficient Se cathode with high Se utilization (97 %) and enhanced Coulombic efficiency. Moreover, with such a designed electrolyte, a highly compact Se electrode (2.35 g_Se cm^?3) with a record‐breaking Se content (80 wt %) and high Se loading (8 mg cm^?2) is demonstrated to have a superhigh volumetric energy density of up to 2502 Wh L^?1, surpassing that of LiCoO₂.     

Solvent Molecule Cooperation Enhancing Lithium Metal Battery Performance at Both Electrodes

Developing electrolytes compatible with efficient and reversible cycling of electrodes is critical to the success of rechargeable Li metal batteries (LMBs). The Coulombic efficiencies and cycle lives of LMBs with ethylene carbonate (EC), dimethyl carbonate, ethylene sulfite (ES), and their combinations as electrolyte solvents show that in a binary‐solvent electrolyte the extent of electrolyte decomposition on the electrode surface is dependent on the solvent component that dominates the solvation sheath of Li⁺. This knowledge led to the development of an EC‐ES electrolyte exhibiting high performance for Li||LiFePO₄ batteries. Carbonate molecules occupy the solvation sheath and improve the Coulombic efficiencies of both the anode and cathode. Sulfite molecules lead to desirable morphology and composition of the solid electrolyte interphase and extend the cycle life of the Li metal anode. The cooperation between these components provides a new example of electrolyte optimization for improved LMBs.     

Fluorine‐Doped Antiperovskite Electrolyte for All‐Solid‐State Lithium‐Ion Batteries

A fluorine‐doped antiperovskite Li‐ion conductor Li₂(OH)X (X=Cl, Br) is shown to be a promising candidate for a solid electrolyte in an all‐solid‐state Li‐ion rechargeable battery. Substitution of F^? for OH^? transforms orthorhombic Li₂OHCl to a room‐temperature cubic phase, which shows electrochemical stability to 9 V versus Li⁺/Li and two orders of magnitude higher Li‐ion conductivity than that of orthorhombic Li₂OHCl. An all‐solid‐state Li/LiFePO₄ with F‐doped Li₂OHCl as the solid electrolyte showed good cyclability and a high coulombic efficiency over 40 charge/discharge cycles.     

Organotrisulfide: A High Capacity Cathode Material for Rechargeable Lithium Batteries

An organotrisulfide (RSSSR, R is an organic group) has three sulfur atoms which could be involved in multi‐electron reduction reactions; therefore it is a promising electrode material for batteries. Herein, we use dimethyl trisulfide (DMTS) as a model compound to study its redox reactions in rechargeable lithium batteries. With the aid of XRD, XPS, and GC‐MS analysis, we confirm DMTS could undergo almost a 4 e^? reduction process in a complete discharge to 1.0 V. The discharge products are primarily LiSCH₃ and Li₂S. The lithium cell with DMTS catholyte delivers an initial specific capacity of 720 mAh g^?1_DMTS and retains 82 % of the capacity over 50 cycles at C/10 rate. When the electrolyte/DMTS ratio is 3:1 mL g^?1, the reversible specific energy for the cell including electrolyte can be 229 Wh kg^?1. This study shows organotrisulfide is a promising high‐capacity cathode material for high‐energy rechargeable lithium batteries.     

A Highly Efficient All‐Solid‐State Lithium/Electrolyte Interface Induced by an Energetic Reaction

The energetic chemical reaction between Zn(NO₃)₂ and Li is used to create a solid‐state interface between Li metal and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) electrolyte. This interlayer, composed of Zn, ZnLi_x alloy, Li₃N, Li₂O, and other species, possesses strong affinities with both Li metal and LLZTO and affords highly efficient conductive pathways for Li⁺ transport through the interface. The unique structure and properties of the interlayer lead to Li metal anodes with longer cycle life, higher efficiency, and better safety compared to the current best Li metal electrodes operating in liquid electrolytes while retaining comparable capacity, rate, and overpotential. All‐solid‐state Li||Li cells can operate at very demanding current–capacity conditions of 4 mA cm^?2–8 mAh cm^?2. Thousands of hours of continuous cycling are achieved at Coulombic efficiency >99.5 % without dendrite formation or side reactions with the electrolyte.     

Advanced High‐Voltage Aqueous Lithium‐Ion Battery Enabled by “Water‐in‐Bisalt” Electrolyte

A new super‐concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra‐high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO₂ as the anode material, and a 2.5 V aqueous Li‐ion cell based on LiMn₂O₄ and carbon‐coated TiO₂ delivered the unprecedented energy density of 100 Wh kg^?1 for rechargeable aqueous Li‐ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the “water‐in‐salt” electrolyte further pushed the energy densities of aqueous Li‐ion cells closer to those of the state‐of‐the‐art Li‐ion batteries.     

An Adjustable‐Porosity Plastic Crystal Electrolyte Enables High‐Performance All‐Solid‐State Lithium‐Oxygen Batteries

The limited triple‐phase boundaries (TPBs) in solid‐state cathodes (SSCs) and high resistance imposed by solid electrolytes (SEs) make the achievement of high‐performance all‐solid‐state lithium‐oxygen (ASS Li‐O₂) batteries a challenge. Herein, an adjustable‐porosity plastic crystal electrolyte (PCE) has been fabricated by employing a thermally induced phase separation (TIPS) technique to overcome the above tricky issues. The SSC produced through the in‐situ introduction of the porous PCE on the surface of the active material, facilitates the simultaneous transfer of Li⁺/e^?, as well as ensures fast flow of O₂, forming continuous and abundant TPBs. The high Li⁺ conductivity, softness, and adhesion of the dense PCE significantly reduce the battery resistance to 115 Ω. As a result, the ASS Li‐O₂ battery based on this adjustable‐porosity PCE exhibits superior performances with high specific capacity (5963 mAh g^?1), good rate capability, and stable cycling life up to 130 cycles at 32 °C. This novel design and exciting results could open a new avenue for ASS Li‐O₂ batteries.     

A Sulfur Heterocyclic Quinone Cathode and a Multifunctional Binder for a High‐Performance Rechargeable Lithium‐Ion Battery

We report a rational design of a sulfur heterocyclic quinone (dibenzo[b,i]thianthrene‐5,7,12,14‐tetraone=DTT) used as a cathode (uptake of four lithium ions to form Li₄DTT) and a conductive polymer [poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)=PEDOT:PSS) used as a binder for a high‐performance rechargeable lithium‐ion battery. Because of the reduced energy level of the lowest unoccupied molecular orbital (LUMO) caused by the introduced S atoms, the initial Li‐ion intercalation potential of DTT is 2.89 V, which is 0.3 V higher than that of its carbon analog. Meanwhile, there is a noncovalent interaction between DTT and PEDOT:PSS, which remarkably suppressed the dissolution and enhanced the conductivity of DTT, thus leading to the great improvement of the electrochemical performance. The DTT cathode with the PEDOT:PSS binder displays a long‐term cycling stability (292 mAh g^?1 for the first cycle, 266 mAh g^?1 after 200 cycles at 0.1 C) and a high rate capability (220 mAh g^?1 at 1 C). This design strategy based on a noncovalent interaction is very effective for the application of small organic molecules as the cathode of rechargeable lithium‐ion batteries.     

A Sustainable Solid Electrolyte Interphase for High‐Energy‐Density Lithium Metal Batteries Under Practical Conditions

High‐energy‐density Li metal batteries suffer from a short lifespan under practical conditions, such as limited lithium, high loading cathode, and lean electrolytes, owing to the absence of appropriate solid electrolyte interphase (SEI). Herein, a sustainable SEI was designed rationally by combining fluorinated co‐solvents with sustained‐release additives for practical challenges. The intrinsic uniformity of SEI and the constant supplements of building blocks of SEI jointly afford to sustainable SEI. Specific spatial distributions and abundant heterogeneous grain boundaries of LiF, LiN_xO_y, and Li₂O effectively regulate uniformity of Li deposition. In a Li metal battery with an ultrathin Li anode (33 μm), a high‐loading LiNi_0.5Co_0.2Mn_0.3O₂ cathode (4.4 mAh cm^?2), and lean electrolytes (6.1 g Ah^?1), 83 % of initial capacity retains after 150 cycles. A pouch cell (3.5 Ah) demonstrated a specific energy of 340 Wh kg^?1 for 60 cycles with lean electrolytes (2.3 g Ah^?1).     

Fast Lithium Ion Conduction in Lithium Phosphidoaluminates

Solid electrolyte materials are crucial for the development of high‐energy‐density all‐solid‐state batteries (ASSB) using a nonflammable electrolyte. In order to retain a low lithium‐ion transfer resistance, fast lithium ion conducting solid electrolytes are required. We report on the novel superionic conductor Li₉AlP₄ which is easily synthesised from the elements via ball‐milling and subsequent annealing at moderate temperatures and which is characterized by single‐crystal and powder X‐ray diffraction. This representative of the novel compound class of lithium phosphidoaluminates has, as an undoped material, a remarkable fast ionic conductivity of 3 mS cm^?1 and a low activation energy of 29 kJ mol^?1 as determined by impedance spectroscopy. Temperature‐dependent ⁷Li NMR spectroscopy supports the fast lithium motion. In addition, Li₉AlP₄ combines a very high lithium content with a very low theoretical density of 1.703 g cm^?3. The distribution of the Li atoms over the diverse crystallographic positions between the [AlP₄]^9? tetrahedra is analyzed by means of DFT calculations.     

Excellent Stability of a Lithium‐Ion‐Conducting Solid Electrolyte upon Reversible Li+/H+ Exchange in Aqueous Solutions

Batteries with an aqueous catholyte and a Li metal anode have attracted interest owing to their exceptional energy density and high charge/discharge rate. The long‐term operation of such batteries requires that the solid electrolyte separator between the anode and aqueous solutions must be compatible with Li and stable over a wide pH range. Unfortunately, no such compound has yet been reported. In this study, an excellent stability in neutral and strongly basic solutions was observed when using the cubic Li₇La₃Zr₂O₁₂ garnet as a Li‐stable solid electrolyte. The material underwent a Li⁺/H⁺ exchange in aqueous solutions. Nevertheless, its structure remained unchanged even under a high exchange rate of 63.6 %. When treated with a 2 M LiOH solution, the Li⁺/H⁺ exchange was reversed without any structural change. These observations suggest that cubic Li₇La₃Zr₂O₁₂ is a promising candidate for the separator in aqueous lithium batteries.     

A High‐Energy‐Density Potassium Battery with a Polymer‐Gel Electrolyte and a Polyaniline Cathode

A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K⁺ ion of the KPF₆ salt is plated/stripped on the potassium‐metal anode. The use of a p‐type polymer cathode increases the cell voltage. By replacing the organic‐liquid electrolyte in a glass‐fiber separator with a polymer‐gel electrolyte of cross‐linked poly(methyl methacrylate), a dendrite‐free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross‐linked architecture provides small pores of adjustable sizes to stabilize a solid‐electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low‐cost potassium batteries for the stationary storage of electric power.     

Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium‐Ion Batteries

Li₇La₃Zr₂O₁₂‐based Li‐rich garnets react with water and carbon dioxide in air to form a Li‐ion insulating Li₂CO₃ layer on the surface of the garnet particles, which results in a large interfacial resistance for Li‐ion transfer. Here, we introduce LiF to garnet Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT‐2 wt % LiF (LLZT‐2LiF) has less Li₂CO₃ on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic‐liquid electrolytes. An all‐solid‐state Li/polymer/LLZT‐2LiF/LiFePO₄ battery has a high Coulombic efficiency and long cycle life; a Li‐S cell with the LLZT‐2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li‐metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.     

Lithium Nitrate Regulated Sulfone Electrolytes for Lithium Metal Batteries

The electrolytes in lithium metal batteries have to be compatible with both lithium metal anodes and high voltage cathodes, and can be regulated by manipulating the solvation structure. Herein, to enhance the electrolyte stability, lithium nitrate (LiNO₃) and 1,1,2,2-tetrafuoroethyl-2′,2′,2′-trifuoroethyl(HFE) are introduced into the high-concentration sulfolane electrolyte to suppress Li dendrite growth and achieve a high Coulombic efficiency of >99 % for both the Li anode and LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathodes. Molecular dynamics simulations show that NO₃⁻ participates in the solvation sheath of lithium ions enabling more bis(trifluoromethanesulfonyl)imide anion (TFSI⁻) to coordinate with Li⁺ ions. Therefore, a robust LiN_xO_y−LiF-rich solid electrolyte interface (SEI) is formed on the Li surface, suppressing Li dendrite growth. The LiNO₃-containing sulfolane electrolyte can also support the highly aggressive LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathode, delivering a discharge capacity of 190.4 mAh g⁻¹ at 0.5 C for 200 cycles with a capacity retention rate of 99.5 %.     

Enhancing the Electrochemical Performance of the LiMn2O4 Hollow Microsphere Cathode with a LiNi0.5Mn1.5O4 Coated Layer

Spinel cathode materials consisting of LiMn₂O₄@LiNi_0.5Mn_1.5O₄ hollow microspheres have been synthesized by a facile solution‐phase coating and subsequent solid‐phase lithiation route in an atmosphere of air. When used as the cathode of lithium‐ion batteries, the double‐shell LiMn₂O₄@LiNi_0.5Mn_1.5O₄ hollow microspheres thus obtained show a high specific capacity of 120 mA h g^?1 at 1 C rate, and excellent rate capability (90 mAhg^?1 at 10 C) over the range of 3.5–5 V versus Li/Li⁺ with a retention of 95 % over 500 cycles.     

Surface Lattice Modulation Enables Stable Cycling of High-Loading All-solid-state Batteries at High Voltages

Halide solid electrolytes, known for their high ionic conductivity at room temperature and good oxidative stability, face notable challenges in all–solid–state Li–ion batteries (ASSBs), especially with unstable cathode/solid electrolyte (SE) interface and increasing interfacial resistance during cycling. In this work, we have developed an Al³⁺–doped, cation–disordered epitaxial nanolayer on the LiCoO₂ surface by reacting it with an artificially constructed AlPO₄ nanoshell; this lithium–deficient layer featuring a rock–salt–like phase effectively suppresses oxidative decomposition of Li₃InCl₆ electrolyte and stabilizes the cathode/SE interface at 4.5 V. The ASSBs with the halide electrolyte Li₃InCl₆ and a high–loading LiCoO₂ cathode demonstrated high discharge capacity and long cycling life from 3 to 4.5 V. Our findings emphasize the importance of specialized cathode surface modification in preventing SE degradation and achieving stable cycling of halide–based ASSBs at high voltages.     

Synergistic Dual-Additive Electrolyte Enables Practical Lithium-Metal Batteries

A rechargeable Li metal anode coupled with a high-voltage cathode is a promising approach to high-energy-density batteries exceeding 300 Wh kg⁻¹. Reported here is an advanced dual-additive electrolyte containing a unique solvation structure and it comprises a tris(pentafluorophenyl)borane additive and LiNO₃ in a carbonate-based electrolyte. This system generates a robust outer Li₂O solid electrolyte interface and F- and B-containing conformal cathode electrolyte interphase. The resulting stable ion transport kinetics enables excellent cycling of Li/LiNi_0.8Mn_0.1Co_0.1O₂ for 140 cycles with 80 % capacity retention under highly challenging conditions (≈295.1 Wh kg⁻¹ at cell-level). The electrolyte also exhibits high cycling stability for a 4.6 V LiCoO₂ (160 cycles with 89.8 % capacity retention) cathode and 4.95 V LiNi_0.5Mn_1.5O₄ cathode.