Tuning Electrolyte Solvation Structure and CEI Film to Enable Long Lasting FSI−-Based Dual-Ion Battery

Dual-ion battery (DIB) is a promising energy storage system because it can provide high power. However, the stability and rate performance of the battery depend strongly on the type of salt and solvents in the electrolyte. Herein, the use of lithium bis(fluorosulfonyl)imide (LiFSI) is studied, which has better high-temperature stability, as salt in the DIB and develop a 3 m  LiFSI fluoroethylene carbonate/methyl 2,2,2-trifluoroethyl carbonate (FEC/FEMC) = 3:7 electrolyte, which stabilizes graphite–lithium DIB with 94.1% capacity retention after 2000 cycles at 5C. The DIB also exhibits excellent rate performance with 100.4 mAh g⁻¹ capacity at 30C, with a utilization of 96.3% compared to capacity at 2C. The outstanding electrochemical performance is attributed to the thin cathode electrolyte interface (CEI) layer and fast FSI⁻ transport kinetics, confirmed by X-ray photoelectron spectroscopy and activation energy calculation. Superior cycle and rate performances are also obtained from a graphite–graphite full cell. Though, increasing salt concentration to 5 and 6 m leads to sluggish FSI⁻ de-intercalation reaction and lower capacity, which is attributed to solvent co-intercalation. The research suggests that the electrolyte plays an important role in ion transport, surface film formation, and stability of DIB.     

Molecular Adsorption-Induced Interfacial Solvation Regulation to Stabilize Graphite Anode in Ethylene Carbonate-Free Electrolytes

Many organic solvents have excellent solution properties, but fail to serve as lithium-ion batteries (LIBs) electrolyte solvents, due to their electrochemical incompatibility with graphite anodes. Herein, a new strategy is proposed to address this issue by introducing a surface-adsorbed molecular layer to regulate the interfacial solvation structure without the alteration of electrolyte composition and properties. As a proof-of-concept study, it is demonstrated for the first time that the intrinsically incompatible propylene carbonate (PC)-based electrolyte becomes completely compatible with graphite anodes by introducing a layer of adsorbed hexafluorobenzene (HFB) molecules to weaken the Li⁺-PC coordination strength and facilitate the interfacial desolvation process. As a consequence, the graphite/ NCM811 pouch cells using the PC-based electrolyte containing only 1 vol.% HFB demonstrate excellent long-term cycling stabilities over 1150 cycles. This strategy is also proved to be applicable to other ethylene carbonate (EC)–free electrolytes, thus providing a new avenue for developing advanced LIB electrolytes.     

Elastic Interfacial Layer Enabled the High-Temperature Performance of Lithium-Ion Batteries via Utilization of Synthetic Fluorosulfate Additive

The key to producing high-energy Li-ion cells is ensuring the interfacial stability of Si-containing anodes and Ni-rich cathodes. Herein, 4-(allyloxy)phenyl fluorosulfate (APFS), a multi-functional electrolyte additive that forms a mechanical strain-adaptive solid electrolyte interphase (SEI) comprising LiF and polymeric species, and a thermally stable cathode–electrolyte interface containing S O and S F species. The radical copolymerization of vinylene carbonate (VC) with APFS via electrochemical initiation creates a spatially deformable polymeric SEI on the SiG-C (30 wt.% graphite + 70 wt.% SiC composite) anode, with large volume changes during cycling. Moreover, the APFS-promoted interfacial layers reduce Ni dissolution and deposition. Furthermore, APFS deactivates the Lewis acid PF₅, thereby inhibiting hydrolyses that produce unwanted HF. These results indicate that the combined use of VC with APFS allows capacity retentions of 72.5% with a high capacity of 143.5 mAh g⁻¹ in SiG-C/LiNi_0.8Co_0.1Mn_0.1O₂ full cells after 300 cycles at 45 °C.     

Synergistic Solvation of Anion: An Effective Strategy toward Economical High-Performance Dual-Ion Battery

The solvation structure of anion plays a crucial role in determining the performance of dual-ion batteries using graphite-positive electrodes. In past research on dual-ion batteries, the design criteria of electrolyte solutions were largely based on the traditional relationship between solvents and additives. Here, a distinctive synergistic solvation strategy is proposed for the design of electrolyte solutions. Despite some solvents performing poorly or even failing to operate when they are used alone for electrolyte solutions, an unexpected improved performance appears when they are combined based on their characteristic moieties. Based on the synergistic solvation strategy, an economical electrolyte solution system (LiPF₆-methyl acetate/diethyl carbonate) is successfully designed. The intercalation behavior of the solvated anion from this solution into the graphite electrode is investigated by conventional electrochemical tests, in situ electrochemical characterizations and theoretical calculations. A proof-of-concept dual-ion battery based on this electrolyte solution delivers a discharge capacity of 100.08 mAh g⁻¹ and ≈4.67 V medium discharge voltage at 10C (1 A g⁻¹), along with 85.35% capacity retention after 1000 cycles at 5C. Moreover, this battery exhibits 93.8% of its room-temperature capacity at −20 °C and can even work at −70 °C. Synergistic solvation offers a novel approach to design electrolyte solutions for dual-ion batteries.     

Electrolytes Enriched by Crown Ethers for Lithium Metal Batteries

Lithium (Li) metal battery is considered the most promising next-generation battery due to its low potential and high theoretical capacity. However, Li dendrite growth causes serious safety problems. Herein, the 15-Crown-5 (15-C-5) is reported as an electrolyte additive based on solvation shell regulation. The strong complex effect between Li⁺ ion and 15-C-5 can reduce the concentration of Li ions on the electrode surface, thus changing the nucleation, and repressing the growth of Li dendrites in the plating process. Significantly, the strong coordination of Li⁺/15-C-5 would be able to make them aggregate around the Li crystal surface, which could form a protective layer and favor the formation of a smooth and dense solid electrolyte interphase with high toughness and Li⁺ ion conductivity. Therefore, the electrolyte system with 2.0 wt% 15-C-5 achieves excellent electrochemical performance with 170 cycles at 1.0 mA cm⁻² with capacity of 0.5 mA h cm⁻² in symmetric Li|Li cells. The obviously enhanced cycle and rate performance are also achieved in Li|LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) full cells. The 15-C-5 demonstrates to be a promising additive for the electrolytes toward safe and efficient Li metal batteries.     

Ultrafast Charging and Stable Cycling Dual-Ion Batteries Enabled via an Artificial Cathode–Electrolyte Interface

Low-cost and environment-friendly dual-ion batteries (DIBs) with fast-charging characteristics facilitate the development of high-power energy storage devices. However, the incompatibility between the cathode and electrolyte at high voltage results in low Coulombic efficiency (CE) and short lifespan. Here, the addition of ≈ 0.5 wt% lithium difluoro(oxalate) borate salt into the electrolyte forms a robust and durable cathode–electrolyte interface (CEI) in situ on the graphite surface, which enables remarkable cycling of the graphite || Li battery with 87.5% capacity retention after 4000 cycles at 5 C and ultrafast rate capability with 88.8% capacity retention under 40 C (4 A g⁻¹), delivering high-power of 0.4–18.8 kW kg⁻¹ at energy densities of 422.7–318.8 Wh kg⁻¹. Taking advantage of this robust CEI, a graphite || graphite full battery demonstrates high reversible capacities of 97.6, 92.8, 88.7, and 85.4 mAh (g cathode)⁻¹ at current rates of 10, 20, 30, and 40 C, respectively. The full battery also shows a long cycling life of over 6500 cycles with 92.4% capacity retention and an average CE of ≈ 99.4% at 1 A g⁻¹, which is superior to other dual-graphite (carbon) batteries in the literature. This work offers an effective interface-stabilizing strategy on protecting graphite cathodes and a promising approach for developing DIBs with high-power capability.     

Ultrafast Charging of a 4.8 V Manganese-Rich Cathode-Based Lithium Metal Cell by Constructing Robust Solid Electrolyte Interphases

Fast charging of Li-metal battery (LMB) is a challenging issue owing to the interfacial instability of Li-metal anode in liquid electrolyte and Li-dendrites growth, resulting in fire hazard. Those issues motivated to pioneer a stabilization strategy of liquid electrolyte-derived solid electrolyte interphase (SEI) layer that enables dendrites-free Li-metal anode under extremely high current density, which solid-state battery cannot. Here, the novel electrolyte formulation is reported including trace-level pentafluoropropionic anhydride (PFPA) combined with fluoroethylene carbonate (FEC) additives, and the SEI stabilization in Li//Mn-rich LMB, achieving unprecedented ultrafast charging under simultaneous extreme conditions of 20 C (charged in 3 min), 4.8 V and 45 °C, delivering 118 mAh g⁻¹ for long reversible 400 cycles, and unprecedented high stability of Li//Li cell under extremely high current 10 mA cm⁻² (Li stripping/plating in 6 min) for a prolonged time of 200 h. The SEI analysis results reveal that the PFPA, which has a symmetric 10 F-containing molecular structure, is a strong F source for promptly producing thin, uniform, and robust F- and organics-enriched SEI layers at both Li-metal anode and Mn-rich cathode, preventing Li-dendrites. This study provides a potential concept for ultrafast charging, long-cycled, and safer high-energy LMBs and LIBs.     

“Water-in-Deep Eutectic Solvent” Electrolytes for High-Performance Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries have been considered as promising alternatives to Li-ion batteries due to their abundant reserves, low price, and high safety. However, Zn anode shows poor reversibility and cycling stability in most conventional aqueous electrolytes. Here, a new type of aqueous Zn-ion electrolyte based on ZnCl₂–acetamide deep eutectic solvent with both environmental and economic friendliness has been prepared. The water molecule introduced in the “water-in-deep eutectic solvent” electrolyte could reduce the Zn²⁺ desolvation energy barrier by regulating Zn²⁺ solvation structure to promote uniform Zn nucleation. Zn anode shows improved electrochemical performance (≈98% Coulombic efficiency over 1000 cycles) in the electrolyte whose molar ratio of ZnCl₂:acetamide:H₂O is 1:3:1. The assembled full battery composed of phenazine cathode and Zn anode could stably cycle over 10 000 cycles with a high capacity retention of 85.7%. Overall, this work offers new insights into exploring new green electrolyte systems for Zn-ion batteries.     

Juggling Formation of HF and LiF to Reduce Crossover Effects in Carbonate Electrolyte with Fluorinated Cosolvents for High-Voltage Lithium Metal Batteries

Fluorinated solvents emerge as a promising strategy to improve performance of lithium metal batteries (LMBs). However, most of them are prone to produce corrosive HF and deteriorate electrode interface, inducing cathode-to-anode detrimental crossover of transition metal-ions. Here, fluorinated aromatic hydrocarbons in dimethyl carbonate (DMC)-based diluted highly concentrated electrolyte (DHCE) are employed to juggle formation of HF and LiF, enabling stable cycling of high-voltage LiNi_0.7Co_0.1Mn_0.2O₂ (NCM712) and LiCoO₂ (LCO). The nature of aromatics in this carbonate-based DHCE makes them difficult to undergo β-hydrogen assisted defluorination, evidencing by the high energy barrier and high bond energy of β-sites hydrogen. The advanced DHCE restrains HF formation but strengthens LiF formation, which not only suppresses impedance growth, transition-metal dissolution, and stress crack on the cathode, but achieves highly reversible Li stripping/plating with an outstanding average Coulombic efficiency up to 99.3%. The Li||NCM712 cell and Li||LCO cell both exhibits superior cycling stability at high operation voltage. Even under stringent conditions, the 4.4 V Li||NCM712 full battery retains >95% of the initial capacity over 100 cycles, advancing practical high-voltage LMBs. This study designs an efficient electrolyte that generates robust electrode/electrolyte interphases and restrains by-products formation spontaneously, thus shedding new light on electrolyte toward applicable LMBs.     

Non-Flammable Electrolyte with Lithium Nitrate as the Only Lithium Salt for Boosting Ultra-Stable Cycling and Fire-Safety Lithium Metal Batteries

Lithium metal batteries (LMBs) attract considerable attention for their incomparable energy density. However, safety issues caused by uncontrollable lithium dendrites and highly flammable electrolyte limit large-scale LMBs applications. Herein, a low-cost, thermally stable, and low environmentally-sensitive lithium nitrate (LiNO₃) is proposed as the only lithium salt to incorporate with nonflammable triethyl phosphate and fluoroethylene carbonate (FEC) co-solvent as the electrolyte anticipated to enhance the performance of LMBs. Benefiting from the presence of NO₃⁻ and FEC with strong solvation effect and easily reduced ability, a Li₃N–LiF-rich stable solid electrolyte interphase is constructed. Compared to commercial electrolytes, the proposed electrolyte has a high Coulombic efficiency of 98.31% in Li-Cu test at 1 mA cm⁻² of 1.0 mAh cm⁻² with dendrite-free morphology. Additionally, the electrolyte system shows high voltage stability and cathode electrolyte interphase film-forming properties with stable cycling performances, which exhibit outstanding capacity retention rates of 96.39% and 83.74% after 1000 cycles for LFP//Li and NCM811//Li, respectively. Importantly, the non-flammable electrolyte delays the onset of combustion in lithium metal soft pack batteries by 255 s and reduces the peak heat release by 21.02% under the continuous external high-temperature heating condition. The novel electrolyte can contribute immensely to developing high-electrochemical-performance and high-safety LMBs.     

Uniform and Multifunctional PEI-POSS/Carbon Encapsulation for High-Rate Performance and Surface Stabilization of Nickel-Rich Layered Cathodes in Lithium-Ion Batteries (Adv. Funct. Mater. 45/2023)

Graphene encapsulation is an attractive surface-coating technology that can simultaneously improve the rate capability and cycle stability of nickel-rich LiNi_xCo_yMn_1−x−yO₂ (NCM). Here, carbon encapsulation with the addition of polyethylenimine (PEI) and polyhedral oligomeric silsesquioxane (POSS), which can effectively suppress access to and generation of harmful factors in the electrolyte to maximize the rate performance and cycle stability of nickel-rich NCM, is described. The PEI-POSS/carbon layer not only facilitates electron and lithium-ion transport on the NCM surface but also inhibits side reactions with the electrolyte during repeated electrochemical reactions. In addition, it provides mechanical support that suppresses the formation of microcracks related to anisotropic volume change of nickel-rich NCM secondary particles and inhibits irreversible phase transitions on surface structures by mitigating electrolyte wettability. As a result, PEI-POSS/carbon-encapsulated NCM exhibits a higher rate capability (84 mAh g⁻¹ at 5 C) and cycle stability (93.5% for 100 cycles at 1 C) compared with bare NCM (0 mAh g⁻¹ at 5 C and 78.4% for 100 cycles at 1 C). In a cycle test at 45 °C, it achieves a capacity retention of 72.6% for 100 cycles at 1 C, which is a 323% improvement in performance over that of bare NCM (22.5%).     

Liberating the Electrolyte via In Situ Conversion of an Amide,Sulfonate-Containing Monomer Precursor for High-Temperature Graphite/NCM Batteries

High-temperature (HT) operation and storage performance of Li-ion batteries (LIBs) are essential for applications in electric vehicles, grid storage, or defense missions. Unfortunately, severe capacity fading is witnessed due to growing instability of the electrode/electrolyte interphase at HT. Herein, the study liberates the electrolyte from the task of film-formation. Instead, it takes advantage of the favorable solid-electrolyte interphase (SEI)-forming functional groups by priorly anchoring them on graphite surface. Specifically, via molecular design, unsaturated CC bond, together with amide and sulfonate groups, are concurrently involved, namely the lithium-2-acrylamido-2-methyl-1-propanesulfonate (Li-AMPS). Upon electrochemical cycle, the unsaturated CC bond in Li-AMPS turns into a radical that induces polymerization between CC bonds to construct a polymeric network. The presence of amide and sulfonate groups endows the SEI with nitrogen, sulfur-based reduction products OSO₂Li and Li₃N, etc. As such, the designed interphase makes the use of propylene carbonate-based electrolyte possible. By assembling full cells with the modified graphite and LiNi_0.5Co_0.2Mn_0.3O₂ (cathode loading of ≈18.5 mg cm⁻²), the capacity retention of the full cell has increased from 53.2% (with pristine graphite) to 77.8% after 300 cycles under 60 °C. A 2 Ah, 265 Wh kg⁻¹ pouch cell is also able to operate for 200 cycles at an extreme temperature of 80 °C with the modified graphite.     

An Intrinsically Nonflammable Electrolyte for Prominent-Safety Lithium Metal Batteries with High Energy Density and Cycling Stability

Nex-generation high-energy-density storage battery, assembled with lithium (Li)-metal anode and nickel-rich cathode, puts forward urgent demand for advanced electrolytes that simultaneously possess high security, wide electrochemical window, and good compatibility with electrode materials. Herein an intrinsically nonflammable electrolyte is designed by using 1 M lithium difluoro(oxalato)borate (LiDFOB) in triethyl phosphate (TEP) and N-methyl-N-propyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [Pyr₁₃][TFSI] ionic liquid (IL) solvents. The introduction of IL can bring plentiful organic cations and anions, which provides a cation shielding effect and regulates the Li⁺ solvation structure with plentiful Li⁺-DFOB⁻ and Li⁺-TFSI⁻ complexes. The unique Li⁺ solvation structure can induce stable anion-derived electrolyte/electrode interphases, which effectively inhibit Li dendrite growth and suppress side reactions between TEP and electrodes. Therefore, the LiNi_0.9Co_0.05Mn_0.05O₂ (NCM90)/Li coin cell with this electrolyte can deliver stable cycling even under 4.5 V and 60 °C. Moreover, a Li-metal battery with thick NCM90 cathode (≈ 15 mg cm⁻²) and thin Li-metal anode (≈ 50 µm) (N/P ≈ 3), also reveals stable cycling performance under 4.4 V. And a 2.2 Ah NCM90/Li pouch cell can simultaneously possess prominent safety with stably passing the nail penetration test, and high gravimetric energy density of 470 Wh kg⁻¹ at 4.4 V.     

Nonpolar Cosolvent Driving LUMO Energy Evolution of Methyl Acetate Electrolyte to Afford Lithium-Ion Batteries Operating at −60 °C

The operation of lithium-ion batteries (LIBs) at low temperatures (<−20 °C) is hindered by the low conductivity and high viscosity of conventional carbonate electrolytes. Methyl acetate (MA) has proven to be a competitive low-temperature electrolyte solvent with low viscosity and low freezing point, but its interfacial stability is poor and remains elusive until now. Here, it is revealed thaat the reductive stability of MA-based electrolytes is fundamentally governed by the anion-prevailed solvation structure. Based on this framework, fluorobenzene is employed in the electrolyte to promote the entry of anions into the solvation shell via dipole-dipole interactions and the generation of free MA, thus enhancing the lowest unoccupied molecular orbital energy of MA. The designed electrolyte enables LiCoO₂ (LCO)/graphite cells to exhibit excellent cycling performance at −20 °C (90% retention after 1000 cycles at 1 C) and to remain 91% of their room-temperature capacity at a super-low temperature of −60 °C at 0.05 C. Thanks to the plentiful free MA, this electrolyte has a high conductivity (2.61 mS cm⁻¹) at −60 °C and allows LCO/graphite cell to charge at −60 °C. This study offers the possibility of practical applications for those solvents with poor reductive stability and provides new approaches to designing advanced electrolytes for low-temperature applications.     

An Aqueous Mg2+-Based Dual-Ion Battery with High Power Density

Rechargeable Mg batteries promise low-cost, safe, and high-energy alternatives to Li-ion batteries. However, the high polarization strength of Mg²⁺ leads to its strong interaction with electrode materials and electrolyte molecules, resulting in sluggish Mg²⁺ dissociation and diffusion as well as insufficient power density and cycling stability. Here an aqueous Mg²⁺-based dual-ion battery is reported to bypass the penalties of slow dissociation and solid-state diffusion. This battery chemistry utilizes fast redox reactions on the polymer electrodes, i.e., anion (de)doping on the polyaniline (PANI) cathode and (de)enolization upon incorporating Mg²⁺ on the polyimide anode. The kinetically favored and stable electrodes depend on designing a saturated aqueous electrolyte of 4.5 m Mg(NO₃)₂. The concentrated electrolyte suppresses the irreversible deprotonation reaction of the PANI cathode to enable excellent stability (a lifespan of over 10 000 cycles) and rate performance (33% capacity retention at 500 C) and avoids the anodic parasitic reaction of nitrate reduction to deliver the stable polyimide anode (86.2% capacity retention after 6000 cycles). The resultant full Mg²⁺-based dual-ion battery shows a high specific power of 10 826 W kg⁻¹, competitive with electrochemical supercapacitors. The electrolyte and electrode chemistries elucidated in this study provide an alternative approach to developing better-performing Mg-based batteries.     

Stable Non-flammable Phosphate Electrolyte for Lithium Metal Batteries via Solvation Regulation by the Additive

The application of lithium metal batteries (LMBs) is impeded by safety concerns. Employing non-flammable electrolytes can improve battery reliability while the cost and performance deterioration limit their popularization. Herein, a high-performance non-flammable electrolyte is designed, 1.5 m LiTFSI in propylene carbonate (PC)/triethyl phosphate (TEP) (4:1 by vol.) with 4-nitrophenyl trifluoroacetate (TFANP) as the additive, which can facilitate the construction of LiF-rich solid electrolyte interphase (SEI) on Li anode surface and cathode electrolyte interphase (CEI) on cathode surface through its prioritized decomposition. In TFANP-containing electrolyte, the decreased TEP coordination number in the solvation sheath relieves the adverse effect of active TEP on both the SEI and CEI for suppressing the growth of Li dendrites and reducing the continuous electrolyte consumption. Thus, the Li||LiNi_0.6Co_0.2Mn_0.2O₂ battery with such an electrolyte can deliver 132 mAh g⁻¹ after 150 cycles with high coulombic efficiency (99.5%) and superior rate performance (110 mAh g⁻¹ at 5 C, 1 C = 200 mA g⁻¹). This work provides a new additive insight on non-flammable electrolyte for reliable LMBs.     

High-Performance All-Solid-State Batteries Enabled by Intimate Interfacial Contact Between the Cathode and Sulfide-Based Solid Electrolytes

All-solid-state batteries (ASSBs) are considered the ultimate next-generation rechargeable batteries due to their high safety and energy density. However, poor Li-ion kinetics caused by the inhomogeneous distribution of the solid electrolytes (SEs) and complex chemo-mechanical behaviors lead to poor electrochemical properties. In this study, LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) (core) – Li₆PS₅Cl (LPSCl) SEs (shell) particles (NCM@LPSCl) are prepared by a facile mechano-fusion method to improve the electrochemical properties and increase the energy density of ASSBs. The conformally coated thin SEs layer on the surface of NCM enables homogeneous distribution of SEs in overall electrode and intimate physical contact with cathode material even under volume change of cathode material during cycling, which leads to the improvement in Li-ion kinetics without the increase in solid electrolyte content. As a result, an ASSBs employing NCM@LPSCl with 4 mAh cm⁻¹ specific areal capacity exhibits robust electrochemical properties, including the improved reversible capacity (163.1 mAh g⁻¹), cycle performance (90.0% after 100 cycles), and rate capability (discharge capacity of 152.69, 133.80, and 100.97 mAh g⁻¹ at 0.1, 0.2, and 0.5 C). Notably, ASSBs employing NCM@LPSCl composite show reliable electrochemical properties with a high weight fraction of NCM (87.3 wt%) in the cathode.     

Catalytically Induced Robust Inorganic-Rich Cathode Electrolyte Interphase for 4.5 V Li||NCM622 Batteries

Tailoring inorganic components of cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) is critical to improving the cycling performance of lithium metal batteries. However, it is challenging due to complicated electrolyte reactions on cathode/anode surfaces. Herein, the species and inorganic component content of the CEI/SEI is enriched with an objectively gradient distribution through employing pentafluorophenyl 4-nitrobenzenesulfonate (PFBNBS) as electrolyte additive guided by engineering bond order with functional groups. In addition, a catalytic effect of LiNi_0.6Mn_0.2Co_0.2O₂ (NCM622) cathode is proposed on the decomposition of PFBNBS. PFBNBS with lower highest occupied molecular orbital can be preferentially oxidized on the NCM622 surface with the help of the catalytic effect to induce an inorganic-rich CEI for superior electrochemical performance at high voltage. Moreover, PFBNBS can be reduced on the Li surface due to its lower lowest unoccupied molecular orbital , increasing inorganic moieties in SEI for inhibiting Li dendrite generation. Thus, 4.5 V Li||NCM622 batteries with such electrolyte can retain 70.4% of initial capacity after 500 cycles at 0.2 C, which is attributed to the protective effect of the excellent CEI on NCM622 and the inhibitory effect of its derived CEI/SEI on continuous electrolyte decomposition.     

Adiponitrile (C6H8N2): A New Bi‐Functional Additive for High‐Performance Li‐Metal Batteries

Rechargeable batteries with a Li metal anode and Ni‐rich Li[Ni_xCo_yMn_1?x?y]O₂ cathode (Li/Ni‐rich NCM battery) have been emerging as promising energy storage devices because of their high‐energy density. However, Li/Ni‐rich NCM batteries have been plagued by the issue of the thermodynamic instability of the Li metal anode and aggressive surface chemistry of the Ni‐rich cathode against electrolyte solution. In this study, a bi‐functional additive, adiponitrile (C₆H₈N₂), is proposed which can effectively stabilize both the Li metal anode and Ni‐rich NCM cathode interfaces. In the Li/Ni‐rich NCM battery, the addition of 1 wt% adiponitrile in 0.8 m LiTFSI + 0.2 M LiDFOB + 0.05 M LiPF₆ dissolved in EMC/FEC = 3:1 electrolyte helps to produce a conductive and robust Li anode/electrolyte interface, while strong coordination between Ni⁴⁺ on the delithiated Ni‐rich cathode and nitrile group in adiponitrile reduces parasitic reactions between the electrolyte and Ni‐rich cathode surface. Therefore, upon using 1 wt% adiponitrile, the Li/full concentration gradient Li[Ni_0.73Co_0.10Mn_0.15Al_0.02]O₂ battery achieves an unprecedented cycle retention of 75% over 830 cycles under high‐capacity loading of 1.8 mAh cm^?2 and fast charge–discharge time of 2 h. This work marks an important step in the development of high‐performance Li/Ni‐rich NCM batteries with efficient electrolyte additives.     

Utilizing Magnetic-Field Modulation to Efficiently Improve the Performance of LiCoO2||Graphite Pouch Full Batteries

The present lithium-ion battery technology competition almost focuses on finding new materials, while less effort is invested in electrode engineering improvement with low-cost. This study proposes a simple method of modulating the preferred orientation of crystal phases in LiCoO₂ electrode using a ≈500 mT magnetic-field, cheaply and efficiently improving the performance of LiCoO₂||graphite pouch full batteries, including cycling stability, rate performance, and thermal safety performance. Under 3.0 C and 45 °C strict test conditions, LiCoO₂-M_⊥||graphite battery even outputs the capacity retention rate of 42.8% after 1000 cycles, while that of pure-LiCoO₂ battery is only 4.4%. Especially, the thermal runaway temperature of the battery needling experiment decreases by considerable 7.7 °C after magnetic-field modulation. Comprehensive characterizations reveal that vertical magnetic field causes spin alignment of LiCoO₂ crystals along the (003) direction. This arrangement effectively improves the Li⁺ diffusion dynamic and the interface compatibility of the electrode, suppressing the electrode polarization. During the cycling processes, the preferred orientation of LiCoO₂ particles forms an enhanced conductive network due to the formation of cross-linked “Li⁺ poor regions” on the surface, ultimately achieving significant performance improvement. This work can provide a potential low-cost strategy for the production of commercial lithium-ion batteries.