Juice Vesicles Bioreactors Technology for Constructing Advanced Carbon-Based Energy Storage.

The construction of high-quality carbon-based energy materials through biotechnology has always been an eager goal of the scientific community. Herein, juice vesicles bioreactors (JVBs) bio-technology based on hesperidium (e.g., pomelo, waxberry, oranges) is first reported for preparation of carbon-based composites with controllable components, adjustable morphologies, and sizes. JVBs serve as miniature reaction vessels that enable sophisticated confined chemical reactions to take place, ultimately resulting in the formations of complex carbon composites. The newly developed approach is highly versatile and can be compatible with a wide range of materials including metals, alloys, and metal compounds. The growth and self-assembly mechanisms of carbon composites via JVBs are explained. For illustration, NiCo alloy nanoparticles are successfully in situ implanted into pomelo vesicles crosslinked carbon (PCC) by JVBs, and their applications as sulfur/carbon cathodes for lithium-sulfur batteries are explored. The well-designed PCC/NiCo-S electrode exhibits superior high-rate properties and enhanced long-term stability. Synergistic reinforcement mechanisms on transportation of ions/electrons of interface reactions and catalytic conversion of lithium polysulfides arising from metal alloy and carbon architecture are proposed with the aid of DFT calculations. The research provides a novel biosynthetic route to rational design and fabrication of carbon composites for advanced energy storage.

High Performance Single-Crystal Ni-Rich Cathode Modification via Crystalline LLTO Nanocoating for All-Solid-State Lithium Batteries.

Sulfide-based all-solid-state lithium batteries (ASSLBs) assembled with Ni-rich layered cathodes are currently promising candidates for achieving high-energy-density and high-safety energy storage systems. However, the interfacial challenges between sulfide electrolyte and Ni-rich layered cathode, such as space charge layer, side reaction, and poor physical contact, greatly limit the practicality of all-solid-state batteries. In this work, an optimal crystalline Li0.35La0.55TiO3 (LLTO) surface coating with a thickness of roughly 6 nm and a high Li ion conductivity of 0.3 mS cm-1 was adopted to enhance the structural stability of the single-crystal LiNi0.6Co0.2Mn0.2O2 (S-NCM622) cathode in ASSLBs. Furthermore, due to the high ionic conductivity and chemical stability of the LLTO coating layer, the interfacial problems, involving interfacial reaction and a space charge layer, in sulfide-based all-solid-state batteries have been effectively solved. As a result, the assembled ASSLBs with the S-NCM622@LLTO cathode exhibit high initial capacity (179.7 mAh g-1) at 0.05 C and excellent cycling performance with 84.5% capacity retention after 100 cycles at 0.1 C at room temperature. This work proposes an effective strategy to enhance the performance of Ni-rich layered cathodes for next-generation high-energy-density sulfide-based lithium batteries.

Heterovalent Cation Substitution to Enhance the Ionic Conductivity of Halide Electrolytes.

Application of halide electrolytes including Li3InCl6 in all-solid-state lithium-metal batteries is still challenging due to the instability with lithium metal and limited ionic conductivity compared with liquid electrolytes and some sulfides. Here, through Zr substitution, a novel Li2.9In0.9Zr0.1Cl6 electrolyte is synthesized through the ball milling and subsequent annealing process. The ionic conductivity of Li2.9In0.9Zr0.1Cl6 (1.54 mS cm-1 at 20 °C) is nearly double that of original Li3InCl6 (0.88 mS cm-1 at 20 °C). Such conductivity enhancement is mainly attributed to the enlarged interplanar spacing and lattice volume, improved concentration of lithium-ion vacancies created by introducing higher-valence Zr4+, and the change of the preferred orientation from the (001) plane to the (131) plane. As a result, the all-solid-state lithium-metal batteries (ASSLMBs) assembled with the Li2.9In0.9Zr0.1Cl6 electrolyte also demonstrate a higher charge/discharge capacity, better cycle stability, and rate performance during cycling without an extra lithium source at the anode side.

Fluorinated Interface Layer with Embedded Zinc Nanoparticles for Stable Lithium-Metal Anodes.

Lithium-metal batteries are promising candidates for the next-generation energy storage devices. However, notorious dendrite growth and an unstable interface between Li and electrolytes severely hamper the practical implantation of Li-metal anodes. Here, a robust solid electrolyte interphase (SEI) layer with flexible organic components on the top and plentiful LiF together with lithiophilic Zn nanoparticles on the bottom is constructed on Li metal based on the spray quenching method. The fluorinated interface layer exhibits remarkable stability to shield Li from the aggressive electrolyte and restrain dendrite growth. Accordingly, the modified Li electrode delivers a stable cycling for over 400 cycles at 3 mA cm-2 in symmetric cells. An improved capacity retention is also achieved in a full cell with a LiFePO4 cathode. This novel design of the artificial SEI layer offers rational guidance for the further development of high-energy-density lithium-metal batteries.

Potassium Hexafluorophosphate Additive Enables Stable Lithium-Sulfur Batteries.

Uncontrollable dendrite growth and low Coulombic efficiency are the two main obstacles that hinder the application of rechargeable Li metal batteries. Here, an optimized amount of potassium hexafluorophosphate (KPF6, 0.01 M) has been added into the 2 M LiTFSI/ether-based electrolyte to improve the cycling stability of lithium-sulfur (Li-S) batteries. Due to the synergistic effect of self-healing electrostatic shield effect from K+ cations and the LiF-rich solid electrolyte interphases derived from PF6- anions, the KPF6 additive enables a high Li Coulombic efficiency of 98.8% (1 mA cm-2 of 1 mAh cm-2). The symmetrical Li cell can achieve a stable cycling performance for over 200 cycles under a high Li utilization up to 33.3%. Meanwhile, the polysulfide shuttle has been restrained due to the higher concentration of the LiTFSI in the electrolyte. As a result, the assembled Li-S full cell displays excellent capacity retention with only 0.25% decay per cycle in the final electrolyte. Our work offers a smart approach to improve both the anode and cathode performance by the electrolyte modification of rechargeable Li-S batteries.

Effect of porous structure on the electrochemical performance of FeS2 for lithium ion batteries.

Porous and solid FeS2 particles are both synthesized via solid-state reaction method using FeC2O4· 2H2O and S powder as the raw materials. The difference of the mophology is adjusted by the calcination time. The porous FeS2 electrode exhibits significantly improved and less improved electrochemical performance comparing to the solid one during the initial 15 cycles and the later cycling process, respectively. The significantly improvement in the initial 15 cycles is due to the large surface area and 3D conducting network of the porous structure, which provides large active electrochemical interface of the active particles and electrolyte, and shortens the path length for Li+ transport. The less improvement during the later cycling process is attributed to the unstable porous structure, which collapses into nanoparticles after long cycles. On the basis of the analysis, a theoretical proposal to optimize the structure of FeS2 electrode is provided.