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It is essential to decouple the interfacial reactions taking place at the anode and cathode in rechargeable batteries. However, due to the reactive nature of Li, it is challenging to use Li‐metal batteries (LMBs) protocol to decouple the interfacial reactions. The by‐products from the anode or cathode become mixed in Li/NMC111 cells, which make decoupling interfacial reactions difficult. Here, reactions at electrodes are successfully decoupled and demystified using a protocol combining anode‐free LMB (AFLMB) with online electrochemical mass spectroscopy. LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) and EC/ethyl methyl carbonate (1:1 v/v%) electrolytes are used to compare interfacial reactions in Li/NMC111 and Cu/NMC111 cells. In Cu/NMC111, the evolution of CO2, CO, and C2H4 gases at the initial stage of first charging is due to interfacial reactions at Cu surface due to solid–electrolyte‐interphase formation. However, the evolution of CO2 and CO gases at high voltage in the entire cycles is associated with chemical and/or electrochemical electrolyte oxidation at the cathode. This work paves a new concept to decouple interfacial reactions at electrodes for developing electrochemically stable electrolytes to improve the performance with the long‐cycling life of AFLMBs and LMBs. [ABSTRACT FROM AUTHOR]

A new lithium-ion battery is configured by coupling sulfurized carbon anode and high voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode. The anode is derived from sulfurized polyacrylonitrile (S-C(PAN)). Severe capacity fading usually becomes unavoidable due to the oxidative decomposition of solvents, primarily when a conventional carbonate electrolyte with 1 M lithium hexafluorophosphate (LiPF 6) is employed. Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and 1, 1, 2, 2-Tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropyl ether (TTE) are formulated as the best electrolyte (3:2:5 in vol. ratio) for this new high-voltage lithium-ion battery to mitigate this capacity fading and improve the adaptability of the S-C(PAN) and LNMO. The discharge capacity of full cell made with 1 M lithium hexafluorophosphate (LiPF 6) in FEC/EMC/TTE (3:2:5) electrolyte reaches 688 mAh g−1 at a rate of 2 C, while 19 mAh g−1 for the control electrolyte. X-ray photoelectron spectroscopy (XPS) results confirm that the fluorinated electrolyte stabilizes both surfaces of S-C(PAN) and LNMO in the full cell effectively. Compared to the control electrolyte, the developed electrolyte enhances the cyclic stability and rate capability of both half cells (Li//S-C(PAN and Li//LiNi 0.5 Mn 1.5 O 4) and S-C(PAN)//LiNi 0.5 Mn 1.5 O 4 full cells. [Display omitted] • Sulfurized polyacrylonitrile anode is paired with high voltage LNMO cathode. • The fluorinated electrolyte consists of carbonates and ether solvents. • FEC/EMC/TTE (vol. 3:2:5) electrolyte results in improved interfacial stability. • LiF-rich CEI on the LNMO suppresses irreversible degradation. • The fluorinated interfaces give high cycling stability and prolonged durability. [ABSTRACT FROM AUTHOR]

A dual-coating process was developed to prepare a unique yolk-shell silicon-reduced graphene oxide/amorphous carbon (YS-Si@rGO/a-C) anode material. The nanostructured Si composite anode material consists of Si cores, evenly wrapped with a first coating of graphene oxide constructed through electrostatic self-assembly, and a shell of a second reinforced coating of graphene oxide/amorphous carbon, integrated by using an economic hydrothermal carbonization process. Thermal reduction and HF etching were then applied to reduce graphene oxide into graphene and to create the required void space to endow the hybrid material with sufficient mechanical strength and to buffer against stresses induced by volume changes of the Si nanoparticles. The obtained YS-Si@rGO/a-C composite anode material has structural integrity together with conductive 3D-network beneficial to its electrochemical performance, attributed to the synergy of electrostatic self-assembly and hydrothermal carbonization. As a result, the composite anode has a superior initial coulombic efficiency of 76 %, surpassing other published Si/G composite anodes, as well as an initial cycle reversible capacity of 1668 mAh g−1 at 0.4 A g−1 and a capacity retention of 75 % after over 100 cycles, when compared with the yolk-shell structured Si@a-C anode. [ABSTRACT FROM AUTHOR]

An investigation of the cycling stability of anode-free batteries (AFBs) using dilute dual-salt electrolytes is conducted in a mixture of ether and carbonate solvents. Using the AFB configuration, various compositions of the dual-salt electrolyte were optimized and it was found that 0.9M-LiTFSI+0.3M-LiDFOB in FEC/TTE (2:3, v/v) is the best. An in-depth investigation of the electrochemical performance of AFB was conducted in this optimized dual-salt composition in comparison to 1.2 M LiTFSI in the same solvent ratio. Accordingly, the performance of Cu||NMC cell in the dual-salt electrolyte surpassed that of the single-salt. The relative better performance of the AFB in the dual-salt electrolyte is attributed to the co-existence of dual-ion (TFSI−&DFOB−) in the electrolyte, which enhanced conductivity and introduces entirely new interphases via preferential decomposition mechanisms. The newly formed interface is stable, ionically conductive, and able to intercept parasitic side reactions between the electrolyte solvent and the deposited Li by blocking electron and solvent flow towards the deposit. As a result of the unique interfacial chemistry brought by this dual-salt system, this electrolyte supports a unique CE (98.6%) and capacity retention (63%) in 4.5V Cu||NMC cell and exhibited >27% improvement over the single salt electrolyte after 50 cycles. [Display omitted] • Dilute dual-salt electrolyte delivers good performance. • Fluorinated salt and solvents result in a compact and stable LiF-rich SEI. • The synergy intercepted electrolyte consumption and gives better Li deposition morphology. • The combined effect gives the cell higher Coulombic efficiency and capacity retention. [ABSTRACT FROM AUTHOR]

Lithium metal has been considered as a potential anode material than those currently used to increase the energy density of lithium ion battery. However, lithium metal anodes suffer from destructive dendrite formation, which causes safety concerns. Anodes with high capacity and safe handling are needed. The sulfurized carbon anode from polyacrylonitrile (S-C(PAN)) composite has been used as a cathode in lithium sulfur batteries. Instead, when the S-C(PAN) is used as an anode and paired with LMO, the full cell delivers an energy density of 185 Wh kg−1 (S-C(PAN)+LMO) at 1 C within the voltage range from 1 to 3.2 V. The full cell (S-C(PAN)||LMO) is characterized by a reversible discharge capacity of 1378 mAh g−1 S and 868 mAh g−1 S at 0.1 C and 2 C, respectively. At 1 C, a retention capacity of 807 mAh g−1 S is achieved at the 400th cycle with an average decay rate of 0.7 mAh g−1 S *cycle−1 and average coulombic efficiency of 99.5%. Interfacial chemistry of S-C(PAN) anode is particularly investigated and S-C(PAN) is demonstrated as one interesting anode material, alternative to lithium metal, due to its high theoretical capacity of sulfur (1675 mAh g−1), environmental friendliness, low cost, and high energy density. Display Omitted • Designed a new cell using S-C(PAN) as anode and LiMn 2 O 4 as cathode. • The S-C(PAN) anode material exhibits good electrochemical performance. • The S-C(PAN).||LMO full cell delivers 868 mAh g−1 S at 2 C. • The S-C(PAN).||LMO cell gives an energy density of 185 Wh kg−1 (S-C(PAN)+LMO) at 1C. • Interfacial and morphological analyses of S-C(PAN) anode are investigated. [ABSTRACT FROM AUTHOR]

Realizing anode free lithium metal battery (AFLMB) is a promising approach to achieve higher energy density without complicated anode chemistry and processing cost. However, uneven lithium (Li) deposition on copper current collector results in dendrite growth and low reversibility. Herein, we report the effect of potassium nitrate (KNO 3) additive to boost the cycling life and average coulombic efficiency (CE) of both full cell (Cu//LiNi 1/3 Mn 1/3 Co 1/3 O 2 or Cu//NMC) and half cell (Cu–Li) configurations. The Cu//NMC cell possesses a capacity retention (CR) of ~40% after 50 cycles in the presence of KNO 3 compared to ~40% after 15 cycles in the control electrolyte, 1 M LiPF 6 in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 v/v). The average CE of Cu//NMC cell with additive for 50 cycles increases to 96.50%, whereas it is 91.32% after 35 cycles without KNO 3. The average efficiencies of Cu–Li cells are 96.20% and 85.74% after 60 cycles with and without KNO 3 respectively. Morphological investigations by Scanning Electron Microscope (SEM) reveal a relatively smooth Li deposition with KNO 3. These achievements originate mainly from (1) new solid electrolyte interphase components from the enhanced reductive decompositions of PF 6 − and NO 3 − and (2) electrostatic shielding effect of K+. Image 1 • KNO 3 containing carbonate electrolyte is prepared. • KNO 3 improves the morphological and electrochemical performance. • Bifunctional KNO 3 contributes new SEI components from NO 3 − reduction. • K+ hinders the dendritic growth of Lithium via electrostatic shielding effect. • KNO 3 facilitates the reductive decomposition of PF 6 − during SEI formation. [ABSTRACT FROM AUTHOR]

Among different types of energy storage devices, anode free battery (AFB) is currently under extensive studies due to its simple configuration, cheap and enhanced energy density. However, a well-known problem like the generation of dendritic lithium and associated safety, poor coulombic efficiency plagues its practical implementations. Here 1.0 M lithium difluoro (oxalate) borate (LiDFOB) + 0.05 M lithium hexafluorophosphate in fluoroethylene carbonate/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether/diethyl carbonate (FEC/TTE/DEC) electrolyte with (2:2:1 v/v/v ratio) delivers better electrochemical performance in both for Cu||LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) as well as for Cu||Li cells compared to FEC/TTE electrolyte with (2:3 v/v ratio). DEC contained and 2:3/FT electrolyte retains about 45% and 8% of the initial discharge capacity after 35 cycles respectively. The average coulombic efficiency of 98.07% for the DEC contained electrolyte after the 35th cycle, while only 92.23% obtained for 2:3/FT. Introducing of DEC results in the improvement of ionic conductivity, the formation of LiF-richer SEI and the formation of more Li on the anode side, which helps the cycle life of the battery. Designing electrolytes based on the synergetic effect from a solvent gives an insight into future pathways to bring solutions to the challenges of an AFB battery. Image 1 • FEC:TTE:DEC (2:2:1) based electrolyte delivers good performance. • DEC solvent improves conductivity of solution. • After 35th cycles, Anode Free Battery gives about 45% retention capacity. • DEC based solvent gives better Li deposition morphology. [ABSTRACT FROM AUTHOR]