Sustainable and Superior Heat-Resistant Alginate Nonwoven Separator of LiNi0.5Mn1.5O4/Li Batteries Operated at 55 °C

Using algae in Li-ion batteries: A sustainable pathway toward greener energy storage

This paper reviews and analyzes the innovations and advances in using algae and their derivatives in different parts of Li-ion batteries. Applications in Li-ion battery anodes, electrolytes, binders, and separators were discussed. Algae provides a sustainable feedstock for different materials that can be used in Li-ion batteries, such as carbonaceous material, biosilica, biopolymers, and other materials that have unique micro- and nano-structures that act as biotemplates for composites structure design. Natural materials and biotemplates provided by algae have various advantages, such as electrochemical and thermal stability, porosity that allows higher storage capacity, nontoxicity, and other properties discussed in the paper. Results reveal that despite algae and its derivatives being a promising renewable feedstock for different applications in Li-ion batteries, more research is yet to be performed to evaluate its feasibility of being used in the industry.

Facile and Powerful In Situ Polymerization Strategy for Sulfur-Based All-Solid Polymer Electrolytes in Lithium Batteries

All-solid-state polymer electrolytes can improve the safety of lithium batteries. However, the common Bellcore polymer electrolyte technology faces several issues such as wasting a mass of solvent, high manufacturing cost, and poor interfacial compatibility between polymer electrolytes and electrodes. Herein, we propose an in situ polymerization technique to synthesize all-solid-state polymer electrolytes by a thiol-Michael addition click reaction. The alternating copolymer is made from the Michael addition reaction of ethylene glycol dimethacrylate (EGDMA) and 1,2-ethane dithiol (EDT). At ambient temperature, the obtained composite polymer electrolyte displays an ionic conductivity of 3.02 × 10^-5 S/cm, an electrochemical window of 4.5 V, and a lithium-ion transference number of 0.45. In light of this unique polymerization process, the traditional fabrication method of liquid electrolyte-based lithium batteries can be adopted in the current study for the preparation of all-solid-state Li/LiFePO₄ batteries. It was found that the assembled all-solid-state Li/LiFePO₄ batteries exhibited superior charging/discharging performance and preferable safety. Thus, this facile and powerful in situ polymerization strategy may open up a new approach for the design and fabrication of all-solid-state batteries with desirable performances.

One-Step Integrated Surface Modification To Build a Stable Interface on High-Voltage Cathode for Lithium-Ion Batteries

As one of the most promising cathode materials for next-generation energy storage applications, spinel LiNi_0.5Mn_1.5O₄ (LNMO) has been highlighted due to many advantages. However, it is still hindered by poor electrochemical stability derived from the bulk/interface structure degradation and side reactions under high working voltage. In this work, fast ion conductor Li₃V₂(PO₄)₃ (LVPO) is adopted to modify the surface of spinel LNMO by a one-step facile method to harvest the maximum benefit of interface properties. It is found that 1 wt % LVPO-LNMO exhibits the most excellent cycling performances, retaining great capacity retention of 87.8% after 500 cycles at room temperature and 82.4% for 150 cycles at 55 °C. Moreover, the rate performance is also significantly improved (90.4 mAh g^-1 under 20C). It is revealed that the LVPO-involved layer could effectively suppress the surface side reactions under high working voltage, which mainly contributes to an improved interface with desirable structural stability and excellent kinetics behavior without sacrificing the surface electrochemical activity in an electrochemical environment. Thus, the dissolution of transition-metal ions is effectively mitigated, avoiding further structure degradation of the bulk material. Especially, it is also established that the vanadium (V) ions in LVPO could be to a certain extent migrated into the surface lattice of LNMO to generate a V-involved transition layer (Li-Ni-Mn-V-O surface solid solution), which greatly co-contributes to the enhanced electrochemical performances owing to the prominently depressed charge-transfer resistance.

Metalophilic Gel Polymer Electrolyte for in Situ Tailoring Cathode/Electrolyte Interface of High-Nickel Oxide Cathodes in Quasi-Solid-State Li-Ion Batteries

High-Ni layered oxides are potential cathodes for high energy Li-ion batteries due to their large specific capacity advantage. However, the fast capacity fade by undesirable structural degradation in liquid electrolyte during long-term cycling is a stumbling block for the commercial application of high-Ni oxides. In this work, a functional gel polymer electrolyte, grafted with sodium alginate, is introduced to increase the stability of high-Ni oxide cathodes at the levels of both the particle and electrode. An in situ generated ion-conducting layer appears on the interface through the chemical interaction between transition-metal cations of the cathode and the metalophilic reticulum group in sodium alginate. Such a tailoring layer can not only enhance the interfacial compatibility on the cathode/electrolyte interface, reducing the interfacial resistance, but also inhibit the HF corrosion, suppressing the dissolution of transition-metal cations and harmful gradient distribution of components through the oxide cathode at the electrode level. Meanwhile, detrimental microcracks in oxide microspheres and between primary crystallites are impressively inhibited at the particle level. The high-Ni oxide cathode with the metalophilic gel polymer electrolyte shows excellent cycle stability with large initial capacity of 204.9 mA h g^-1 at a 1.0 C rate and high discharge capacity retention within 300 cycles at high temperature.

Electrospun Flexible Cellulose Acetate-Based Separators for Sodium-Ion Batteries with Ultralong Cycle Stability and Excellent Wettability: The Role of Interface Chemical Groups

Na-ion batteries are one of the best technologies for large-scale applications depending on almost infinite and widespread sodium resources. However, the state-of-the-art separators cannot meet the engineering needs of large-scale sodium-ion batteries to match the intensively investigated electrode materials. Here, a kind of flexible modified cellulose acetate separator (MCA) for sodium-ion batteries was synthesized via the electrospinning process and subsequently optimizing the interface chemical groups by changing acetyl to hydroxyl partly. Upon the rational design, the flexible MCA separator exhibits high chemical stability and excellent wettability (contact angles nearly 0°) in electrolytes (EC/PC, EC/DMC, diglyme, and triglyme). Moreover, the flexible MCA separator shows high onset temperature of degradation (over 250 °C) and excellent thermal stability (no shrinkage at 220 °C). Electrochemical measurements, importantly, show that the Na-ion batteries with flexible MCA separator exhibit ultralong cycle life (93.78%, 10 000 cycles) and high rate capacity (100.1 mAh g^-1 at 10 C) in the Na/Na₃V₂(PO₄)₃ (NVP) half cell (2.5-4.0 V) and good cycle performance (98.59%, 100 cycles) in the Na/SnS₂ half cell (0.01-3 V), respectively. Moreover, the full cell (SnS₂/NVP) with flexible MCA separator displays the capacity of 98 mAh g^-1 and almost no reduction after 40 cycles at 0.118 A g^-1. Thus, this work provides a kind of flexible modified cellulose acetate separator for Na-ion batteries with great potential for practical large-scale applications.

Cellulose ultrafine fibers embedded with titania particles as a high performance and eco-friendly separator for lithium-ion batteries

Mixtures of cellulose acetate (M.W. ∼3 × 10⁴ g/mol) dissolved in 75% v/v acetic acid in water (17% w/w) and ground anatase titania particles with diameters of 197 ± 75 nm (0%, 5% and 10% w/w) were electrospun at 17 kV with a fiber collection distance and a feed rate of 10 cm and 0.6 mL/h. Then, the fiber was treated with 0.5 M potassium hydroxide in ethanol. Rough regenerated cellulose (RC)-titania separators with diameters of ∼310 nm and uniformly dispersed titania particles showed ∼78% porosities. They decomposed at 300 °C, higher than the decomposition temperature of polyethylene separators (220 °C). Added titania particles increased the electrolyte wettability and lithium transference number (from 0.22 to 0.62). RC - 10% titania separator retained the capacity with 79 mA h/g after 30 cycles and had excellent discharge capacity. These fascinating properties make RC-titania separator promising for lithium ion battery.

Cellulosic Biomass-Reinforced Polyvinylidene Fluoride Separators with Enhanced Dielectric Properties and Thermal Tolerance

Safety issues are critical barriers to large-scale energy storage applications of lithium-ion batteries (LIBs). Using an ameliorated, thermally stable, shutdown separator is an effective method to overcome the safety issues. Herein, we demonstrate a novel, cellulosic biomass-material-blended polyvinylidene fluoride separator that was prepared using a simple nonsolvent-induced phase separation technique. This process formed a microporous composite separator with reduced crystallinity, uniform pore size distribution, superior thermal tolerance, and enhanced electrolyte wettability and dielectric and mechanical properties. In addition, the separator has a superior capacity retention and a better rate capability compared to the commercialized microporous polypropylene membrane. This fascinating membrane was fabricated via a relatively eco-friendly and cost-effective method and is an alternative, promising separator for high-power LIBs.