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1. Natural protein as novel additive of a commercial electrolyte for Long-Cycling lithium metal batteries

   https://doi.org/10.1016/j.cej.2022.135283  

   Wang, Chenxu ; Fu, Xuewei ; Ying, Chunhua ; Liu, Jin ; Zhong, Wei-Hong ( February 2022 , Chemical engineering journal)

   Suffering from critical instability of lithium (Li) anode, the most commercial electrolytes, carbonate-ester electrolytes, have been restrictedly used in high-energy Li metal batteries (LMBs) despite of their broad implementation in lithium-ion batteries. Here, abundant, natural corn protein, zein, is exploited as a novel additive to stabilize Li anode and effectively prolong the cycling life of LMBs based on carbonate-ester electrolyte. It is discovered that the denatured zein is involved in the formation of solid electrolyte interphase (SEI), guides Li+ deposition and repairs the cracked SEI. In specific, the zein-rich SEI benefits the anion immobilization, enabling uniform Li+ deposition to diminish dendrite growth; the preferential zein-Li reaction effectively repairs the cracked SEI, protecting Li from parasite reactions. The resulting symmetrical Li cell exhibits a prolonged cycling life to over 350 h from <200 h for pristine cell at 1 mA cm􀀀 2 with a capacity of 1 mAh cm^ 2. Paired with LiFePO4 cathode, zein additive markedly improves the electrochemical performance including a higher capacity of 130.1 mAh g^ 1 and a higher capacity retention of ~ 80 % after 200 cycles at 1 C. This study demonstrates a natural protein to be an effective additive for the most commercial electrolytesmore »for advancing performance of LMBs.« less
2. Universal Cathode Design Strategies to Engineer Cathode Electrolyte Interfaces for High Performance All-Solid-State Batteries

   Zhang, Yuxuan ; Song, Han Wook ; Lee, Sunghwan ( May 2022 , Materials Research Society)

   Metal-ion batteries (e.g., lithium and sodium ion batteries) are the promising power sources for portable electronics, electric vehicles, and smart grids. Recent metal-ion batteries with organic liquid electrolytes still suffer from safety issues regarding inflammability and insufficient lifetime.1 As the next generation energy storage devices, all-solid-state batteries (ASSBs) have promising potentials for the improved safety, higher energy density, and longer cycle life than conventional Li-ion batteries.2 The nonflammable solid electrolytes (SEs), where only Li ions are mobile, could prevent battery combustion and explosion since the side reactions that cause safety issues as well as degradation of the battery performance are largely suppressed. However, their practical application is hampered by the high resistance arising at the solid–solid electrode–electrolyte interface (including cathode-electrolyte interface and anode-electrolyte interface).3 Several methods have been introduced to optimize the contact capability as well as the electrochemical/chemical stability between the metal anodes (i.e.: Li and Na) and the SEs, which exhibited decent results in decreasing the charge transfer resistance and broadening the range of the stable energy window (i.e., lowing the chemical potential of metal anode below the highest occupied molecular orbital of the SEs).4 Nevertheless, mitigation for the cathode in ASSB is tardily developed because: (1) themore »porous structure of the cathode is hard to be infiltrated by SEs;5 (2) SEs would be oxidized and decomposed by the high valence state elements at the surface of the cathode at high state of charge.5 Herein, we demonstrate a universal cathode design strategy to achieve superior contact capability and high electrochemical/chemical stability with SEs. Stereolithography is adopted as a manufacturing technique to realize a hierarchical three-dimensional (HTD) electrode architecture with micro-size channels, which is expected to provide larger contact areas with SEs. Then, the manufactured cathode is sintered at 700 °C in a reducing atmosphere (e.g.: H2) to accomplish the carbonization of the resin, delivering sufficiently high electronic conductivity for the cathode. To avoid the direct exposure of the cathode active materials to the SEs, oxidative chemical vapor deposition technique (oCVD) is leveraged to build conformal and highly conducting poly(3,4-ethylenedioxythiophene) (PEDOT) on the surface of the HTD cathode.6 To demonstrate our design strategy, both NCM811 and Na3V2(PO4)3 is selected as active materials in the HTD cathode, then each cathode is paired with organic (polyacrylonitrile-based) and inorganic (sulfur-based) SEs assembled into two batteries (total four batteries). SEM and TEM reveal the micro-size HTD structure with built-in channels. Featured by the HTD architecture, the intrinsic kinetic and thermodynamic conditions will be enhanced by larger surface contact areas, more active sites, improved infusion and electrolyte ion accessibility, and larger volume expansion capability. Disclosed by X-ray computed tomography, the interface between cathode and SEs in the four modified samples demonstrates higher homogeneity at the interface between the cathode and SEs than that of all other pristine samples. Atomic force microscopy is employed to measure the potential image of the cross-sectional interface by the peak force tapping mode. The average potential of modified samples is lower than that of pristine samples, which confirms a weakened space charge layer by the enhanced contact capability. In addition, through Electron Energy Loss Spectroscopy coupled with Scanning Transmission Electron Microscopy, the preserved interface between HTD cathode and SE is identified; however, the decomposing of the pristine cathode is clearly observed. In addition, Finite element method simulations validate that the diffusion dynamics of lithium ions is favored by HTD structure. Such a demonstrated universal strategy provides a new guideline to engineer cathode electrolyte interface by reconstructing electrode structures that can be applicable to all solid-state batteries in a wide range of chemical conditions.« less
3. Anisotropic mass transport using ionic liquid crystalline electrolytes to suppress lithium dendrite growth

   https://doi.org/10.1039/d0se01547d  

   Gopalakrishnan, Deepesh ; Alkatie, Samia ; Cannon, Andrew ; Rajendran, Sathish ; Thangavel, Naresh Kumar ; Bhagirath, Neha ; Ryan, Emily M. ; Arava, Leela Mohana ( March 2021 , Sustainable Energy & Fuels)

   Lithium metal as an anode has been widely accepted due to its higher negative electrochemical potential and theoretical capacity. Nevertheless, the existing safety and cyclability issues limit lithium metal anodes from practical use in high-energy density batteries. Repeated Li deposition and dissolution processes upon cycling lead to the formation of dendrites at the interface which results in reduced Li availability for electrochemical reactions, disruption in Li transport through the interface and increased safety concerns due to short circuiting. Here, we demonstrate a novel strategy using Ionic Liquid Crystals (ILCs) as the electrolyte cum pseudo-separator to suppress dendrite growth with their anisotropic properties controlling Li-ion mass transport. A thermotropic ILC with two-dimensional Li-ion conducting pathways was synthesized and characterized. Microscopic and spectroscopic analyses elucidate that the ILC formed with a smectic A phase, which can be utilized for wide temperature window operation. The results of electrochemical studies corroborate the efficacy of ILC electrolytes in mitigating dendrite formation even after 850 hours and it is further substantiated by numerical simulation and the mechanism involved in dendritic suppression was deduced.
4. High-performance all-solid-state batteries enabled by salt bonding to perovskite in poly(ethylene oxide)

   https://doi.org/10.1073/pnas.1907507116  

   Xu, Henghui ; Chien, Po-Hsiu ; Shi, Jianjian ; Li, Yutao ; Wu, Nan ; Liu, Yuanyue ; Hu, Yan-Yan ; Goodenough, John B. ( September 2019 , Proceedings of the National Academy of Sciences)

   Flexible and low-cost poly(ethylene oxide) (PEO)-based electrolytes are promising for all-solid-state Li-metal batteries because of their compatibility with a metallic lithium anode. However, the low room-temperature Li-ion conductivity of PEO solid electrolytes and severe lithium-dendrite growth limit their application in high-energy Li-metal batteries. Here we prepared a PEO/perovskite Li 3/8 Sr 7/16 Ta 3/4 Zr 1/4 O 3 composite electrolyte with a Li-ion conductivity of 5.4 × 10 −5 and 3.5 × 10 −4 S cm −1 at 25 and 45 °C, respectively; the strong interaction between the F − of TFSI − (bis-trifluoromethanesulfonimide) and the surface Ta 5+ of the perovskite improves the Li-ion transport at the PEO/perovskite interface. A symmetric Li/composite electrolyte/Li cell shows an excellent cyclability at a high current density up to 0.6 mA cm −2 . A solid electrolyte interphase layer formed in situ between the metallic lithium anode and the composite electrolyte suppresses lithium-dendrite formation and growth. All-solid-state Li|LiFePO 4 and high-voltage Li|LiNi 0.8 Mn 0.1 Co 0.1 O 2 batteries with the composite electrolyte have an impressive performance with high Coulombic efficiencies, small overpotentials, and good cycling stability.
5. A Janus protein-based nanofabric for trapping polysulfides and stabilizing lithium metal in lithium–sulfur batteries

   https://doi.org/10.1039/d0ta01989e  

   Chen, Min ; Chen, Zhiping ; Fu, Xuewei ; Zhong, Wei-Hong ( April 2020 , Journal of Materials Chemistry A)

   The shuttling of polysulfides and uncontrollable growth of lithium dendrites remain the most critical obstacles deteriorating the performance and safety of lithium–sulfur batteries. The separator plays a key role in molecule diffusion and ion transport kinetics; thus, endowing the separator with functions to address the two abovementioned issues is an urgent need. Herein, a protein-based, low-resistance Janus nanofabric is designed and fabricated for simultaneously trapping polysulfides and stabilizing lithium metal. The Janus nanofabric is achieved via combining two functional nanofabric layers, a gelatin-coated conductive nanofabric (G@CNF) as a polysulfide-blocking layer and a gelatin nanofabric (G-nanofabric) as an ion-regulating layer, into a heterostructure. The gelatin coating of G@CNF effectively enhances the polysulfide-trapping ability owing to strong gelatin–polysulfide interactions. The G-nanofabric with exceptional wettability, high ionic conductivity (4.9 × 10 −3 S cm −1 ) and a high lithium-ion transference number (0.73) helps stabilize ion deposition and thus suppresses the growth of lithium dendrites. As a result, a Li/Li symmetric cell with the G-nanofabric delivers ultra-long cycle life over 1000 h with very stable performance. Benefiting from the synergistic effect of the two functional layers of the Janus nanofabric, the resulting Li–S batteries demonstrate excellent capacity, rate performance and cycling stability (more »e.g. initial discharge capacity of 890 mA h g −1 with a decay rate of 0.117% up to 300 cycles at 0.5 A g −1 ).« less