Double-Protected Layers with Solid-Liquid Hybrid Electrolytes for Long-Cycle-Life Lithium Batteries.

Lithium-ion batteries (LIBs) with liquid electrolytes (LEs) have problems such as electrolyte leakage, low safety profiles, and low energy density, which limit their further development. However, LIBs with solid electrolytes are safer with better energy and high-temperature performance. Thus, solid electrolyte system batteries have attracted widespread attention. However, due to the inherent rigidity of the LATP solid electrolyte, there is a high interface impedance at the LATP/electrode. In addition, the Ti element in LATP easily reacts with the Li metal. Here, we dripped an LE at the LATP/electrode interface (solid-liquid hybrid electrolytes) to reduce its interface impedance. A composite polymer electrolyte (CPE) protective film (containing PVDF, SN, and LiTFSI) was then cured in situ at the LATP/Li interface to avoid side reactions of LATP. The discharge specific capacity of the LiFePO4/LATP-12% LE-CPE/Li system is up to 150 mAh g-1, and the capacity retention rate is still 96% after 250 cycles. In addition, the NCM622/PVDF-LATP-12% LE/Li system has an initial reversible capacity of 170 mAh g-1. This study reports an approach that can protect solid electrolytes from lithium metal instability.

Effect of Organic Electrolyte on the Performance of Solid Electrolyte for Solid-Liquid Hybrid Lithium Batteries.

The interface problem caused by the contact between the electrodes and the solid electrolyte was the main factor hindering the development of solid-state batteries. To enhance the electrode|solid electrolyte interface property, we designed a hybrid electrolyte, the combination of x vol % Li1.3Al0.3Ti1.7(PO4)3 (LATP) inorganic solid electrolyte and 1 - x vol % liquid organic electrolyte (LE). In this work, the 1 - x vol % LE was dropped between the electrode and the solid electrolyte, and it is found that the electrochemical performance of the LiFePO4|Li solid-liquid hybrid battery is significantly improved. At the current density of 0.1 and 0.5 C, the LATP with 15% liquid organic electrolyte could deliver a specific capacity of 160.5 and 124.3 mAh g-1, respectively; moreover, the specific discharge capacity remained as high as 111 mAh g-1 at 0.5 C after 100 cycles, indicating that the larger interface impedance was eliminated. The LE may have three functions: (1) forming a solid-liquid electrolyte interphase on the surface of the LATP particles to prevent further reduction of LATP, (2) wetting the electrode and solid electrolyte to reduce the interface resistance, and (3) improving interfacial Li-ion transport.

Reducing interfacial resistance of a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte/electrode interface by polymer interlayer protection.

High interfacial resistance of an electrode/electrolyte interface is the most challenging barrier for the expanding application of all-solid-state lithium batteries (ASSLBs). To address this challenge, poly(propylene carbonate)-based solid polymer electrolytes (PPC-SPEs) were introduced as interlayers combined with a Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid state electrolyte (SSE), which successfully decreased the interfacial resistance of the SSE/electrolyte interface by suppressing the reduction reaction of Ge4+ against the Li metal, as well as producing intimate contact between the cathode and electrolyte. This work provides a systematic analysis of the interfacial resistance of the cathode/SSE, Li/SSE and the polymer/LAGP interfaces. As a consequence, the interfacial resistance of the Li/SSE interface decreased about 35%, and the interfacial resistance of the cathode/SSE interface decreased from 3.2 × 104 to 543 Ω cm2. With a PPC-LAGP-PPC sandwich structure composite electrolyte (PLSSCE), the all-solid-state LiFePO4/Li cell showed a high capacity of 148.1 mA h g-1 at 0.1C and a great cycle performance over 90 cycles.

Self-Sacrificed Interface-Based on the Flexible Composite Electrolyte for High-Performance All-Solid-State Lithium Batteries.

Ceramic electrolyte guarantees the commercial application of all-solid-state lithium batteries (ASSLBs) for its high ionic conductivity and wide voltage window. However, the large interfacial impedance between the ceramic and polymeric electrolyte is still tough issue for all-solid-state batteries. Here, a "self-sacrifice" interface established by a flexible Li1.5Al0.5Ge1.5(PO4)3 (LAGP)/30% poly(propylene carbonate) (PPC) solid composite electrolyte causes a performance enhancement of the LiFePO4/Li battery with a discharge specific capacity of 151 mA h g-1 at 0.05 C and a retention of 92.3% for 100 cycles at 55 °C without any liquid electrolyte, where the PPC-derived layer swells the Li metal and infiltrates to develop the amorphous state to reduce both interfacial and bulk resistance; while the LAGP with good mechanical strength and the LiF layer provides stability and resists the growth of Li dendrites, which guaranteed the long cycle life and security of batteries. This study demonstrates the complementary advantages of ceramic and polymer, which implies a feasible way to achieve a well-wetted, soft, and stable contact of the electrolyte and electrode to overcome the interface issues in ASSLBs.

A Highly Active CoFe Layered Double Hydroxide for Water Splitting.

Highly active, cost-effective, and durable catalysts for oxygen evolution reaction (OER) are required in energy conversion and storage processes. A facile synthesis of CoFe layered double hydroxide (CoFe LDH) is reported as a highly active and stable oxygen evolution catalyst. By varying the concentration of the metal ion precursor, the Co/Fe ratios of LDH products can be tuned from 0.5 to 7.4. The structure and electrocatalytic activity of the obtained catalysts were found to show a strong dependence on the Co/Fe ratios. The Co2 Fe1 LDH sample exhibited the best electrocatalytic performance for OER with an onset potential of 1.52 V (vs. the reversible hydrogen electrode, RHE) and a Tafel slope of 83 mV dec-1 . The Co2 Fe1 LDH was further loaded onto a Ni foam (NF) substrate to form a 3D porous architecture electrode, offering a long-term current density of 100 mA cm-2 at 1.65 V (vs. RHE) towards the OER.