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Here we report an ‘injection’ strategy to introduce transportable Li-ion in the metallic Li free sulfur-graphite (S-G) pouch type full cell, which could alleviate the safety issues from Li dendrites. A novel process with organolithium reagent is used to reduce S to Li2S rapidly during assembling the pouch type full cell. The sublimation property of the side product enables the in-situ injection in the pouch type cell, which will not introduce impurities. In addition, this ‘injection’ strategy avoids the drawbacks from the instability of the Li2S to moisture, which could largely reduce the production cost and improve the practical energy density of the cell. The injected Li2S-G battery shows quite stable cyclability with a capacity of 640 mAh g−1 at 0.1 C rate. This in-situ ‘injection’ method provides an effective and practical way to produce Li metal free sulfur Li-ion battery with alleviated safety issues.

Lithium-ion batteries are required to have high-power density, that is to reduce impedance, for use in electric vehicles. This paper focuses on interfacial resistance between the cathode layer (CL) and the current collector (CC) observed at high frequencies, which is generally attributed to a resistance of surface film like SEI. To investigate the interfacial resistance systematically, different interfaces between the CL and the CC were prepared by controlling the press rate for the cathode preparation, or by introducing a carbon under-coating layer (CUL), followed by electrochemical impedance spectroscopy (EIS). The interfacial resistance between the CL and the CC prepared with an insufficient press rate or without a CUL was extremely high for the entire cathode. From the cathode cross-sectional observation, it was observed that this high interfacial resistance was caused by low contact rate at the interface. Using a pouch-type symmetric cell, EIS revealed that the interfacial resistance is attributed to electric resistance, that is, contact resistance at the interface. Also, the other resistances were attributed to be the ionic resistance of the electrolyte and pores in the cathode, and the charge transfer resistance of the cathode. Furthermore, the effectiveness of the CUL was shown to decrease the cathode impedance.

A system using a high-speed and high-precision X-ray inspection system for testing internal short circuits in lithium-ion batteries (LIBs) was firstly developed for the safety test on LIBs. X-ray transmission moving images of the anode and cathode were obtained in the layered LIB structure. The nail-penetration test was chosen to test for the presence of an internal short circuit. This system would allow direct observation of smoke generation inside outside the battery, ballooning of the pouch, as well as changing layered structures of electrodes in real time. Since the results of a conventional nail-penetration test are indicated only by smoke generation, fire, or explosion, this new system allows electrode changes in the pouch to be observed for the first time. This system is expected to lead to great developments in the safety of LIBs.

Sulfur (S) Li-ion battery which use the metallic Li free anode is deemed as a promising solution to conquer the hazards originating from Li metal. However, stable cycling performance and low production price of the S Li-ion battery still remain challenging. Here, we propose a S-LixC full cell system by paring a S cathode and a pre-lithiated graphite anode which is cheap and commercially available. It shows stable cycling performance with a capacity around 1300 mAh (g-S)−1 at 0.2 C-rate and 1000 mAh (g-S)−1 at 0.5 C-rate. In addition, 0.1% per cycle capacity fading rate with a capacity retention of 880 mAh (g-S)−1 after 400 cycles at 0.2 C-rate has been achieved. The pre-formed solid electrolyte interphase (SEI) layer on the pre-lithaited graphite anode largely contributes to the high capacity performance. Notably, a 10-times-enlarged scale of S-LixC laminate type full cell has been assembled with high capacity performance (around 1000 mAh (g-S)−1) even after high rate cycling.

This work reports a new chemical pre-lithiation method to fabricate lithium sulfide (Li2S) cathode. This pre-lithiation process is taken place simply by dropping the organolithium reagent lithium naphthalenide (Li+Naph−) on the prepared sulfur cathode. It is the first time realizing the room temperature chemical pre-lithaition reaction attributed by the 3D nanostructured carbon nanotube (CNT) current collector. It is confirmed that the Li2S cathode fabricated at room temperature showing higher capacity and lower hysteresis than the Li2S cathode fabricated at high temperature pre-lithiation. The pre-lithiated Li2S cathode at room temperature shows stable cycling performance with a 600 mAh g−1 capacity after 100 cycles at 0.1 C-rate and high capacity of 500 mAh g−1 at 2 C-rate. This simple on-site pre-lithiation method at room temperature is demonstrated to be applicable for the in-situ pre-lithiation in a Li metal free battery.

Organic-inorganic lead halide perovskite solar cells have received global attention, and their upscaling to perovskite solar modules under ambient conditions merits investigation. Herein, an upscaled mini-module consisting of five serially interconnected cells demonstrate a power conversion efficiency of 6.18% measured on an aperture area of 10.4 cm2. The perovskite photovoltaic mini-module with an inverted configuration is realized on a 5 × 5.5 cm2 ITO glass substrate using a technique combining ultrasonic spray-coating of both the NiOx hole transport layer (HTL) and perovskite photoabsorber layer with mechanical scribing for module patterning. The influence of the post-annealing duration (3, 5, 8, 10, and 15 min) of the spray-coated NiOx films under optimized fabrication conditions of the perovskite mini-module is investigated. The bulk properties of the NiOx thin films as functions of annealing time and their interfacial properties with methylammonium lead iodide (MAPbI3) are comprehensively discussed. The use of spray-coating to assemble the NiOx HTL/perovskite photoactive layer of the mini-module demonstrate the significant potential of this technique to facilitate scalable production of perovskite-based photovoltaic modules.

Lithium metal free sulfur battery paired by lithium sulfide (Li2S) is a hot point in recent years because of its potential for relatively high capacity and its safety advantage. Due to the insulating nature and high sensitivity to moisture of Li2S, it calls for new way to introduce Li ion into S cathode besides the method of directly using the Li2S powder for the battery pre-lithiation. Herein, we proposed a pre-lithiation method to lithiate the polypyrrole (PPy)/S/Ketjenblack (KB) electrode into PPy/Li2S/KB cathode at room temperature. By this process, the fully lithiated PPy/Li2S/KB cathode showed facilitated charge transfer than the original PPy/S/KB cathode, leading to better cycling performance at high C-rates and disappearance of over potential phenomenon. In this work, the ion-selective PPy layer has been introduced on the cathode surface by an electrodeposition method, which can suppress the polysulfide dissolution from the cathode source. The lithium metal free full battery coupled by the prepared Li2S/KB cathode and graphite anode exhibited excellent cycling performance. Hence, we believe this comprehensive fabrication approach of Li2S cathode will pave a way for the application of new type lithium metal free secondary battery.

In this study, we report the preparation of carbon nanotubes (CNTs) anchor layer on a Cu substrate (CNTs/Cu) by using electrophoretic deposition technique. The CNTs anchor layer increases adhesion strength between Si-O-C composites and Cu substrate, as a result, it is possible to improve deposited Si amounts and areal capacity. The electrodeposited Si-O-C composites on CNTs/Cu (Si-O-C/CNTs/Cu) show homogenously coated surface morphology without cracks even large passing charge for electrodeposition of 15 C cm−2, resulting in 0.21 mg cm−2 of deposited Si amounts. On the other hand, Si-O-C composites deposited on as-received Cu substrate (Si-O-C/Cu) begin to peel off from substrate at 8 C cm−2 of passing charge, resulting in 0.13 mg cm−2 of deposited Si amounts, and decrease down to 0.10 mg cm−2 at 15 C cm−2 of passing charge. As a results, the improved Si amounts deposited on CNTs/Cu substrate achieve higher areal capacity, delivering 0.24 mA h cm−2, which attains increase in 84.6% in comparison to Si-O-C/Cu, which has areal capacity of 0.13 mA g cm−2 at 8 C cm−2 of passing charge. Moreover, the Si-O-C/CNTs/Cu shows improved anode performances including discharge capacity and C-rate performance of the Si-O-C composites than Si-O-C/Cu without CNTs anchor layer.

Stable charge–discharge cycling behavior for a lithium metal anode in a dimethylsulfoxide (DMSO)–based electrolyte is strongly desired of lithium–oxygen batteries, because the Li anode is rapidly exhausted as a result of side reactions during cycling in the DMSO solution. Herein, we report a novel electrolyte design for enhancing the cycling performance of Li anodes by using a highly concentrated DMSO-based electrolyte with a specific Li salt. Lithium nitrate (LiNO 3 ), which forms an inorganic compound (Li 2 O) instead of a soluble product (Li 2 S) on a lithium surface, exhibits a >20% higher coulombic efficiency than lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate, regardless of the loading current density. Moreover, the stable cycling of Li anodes in DMSO-based electrolytes depends critically on the salt concentration. The highly concentrated electrolyte 4.0 M LiNO 3 /DMSO displays enhanced and stable cycling performance comparable to that of carbonate-based electrolytes, which had not previously been achieved. We suppose this enhancement is due to the absence of free DMSO solvent in the electrolyte and the promotion of the desolvation of Li ions on the solid electrolyte interphase surface, both being consequences of the unique structure of the electrolyte.

The effect of the solid electrolyte interphase (SEI) on a Li anode on the charge–discharge cycling performance in 1 M LiTFSI/dimethylsulfoxide electrolyte solution is examined by using charge–discharge cycling. The chemical structure of the surface and interior of the SEI strongly affects the cycling performance of the anode. The observed coulombic efficiency is low ( 2 CO 3 , Li 2 O, and LiF form instead, the coulombic efficiency increases to >85%. This enhanced efficiency remains constant regardless of the O 2 content and despite 2 O in the electrolyte. Thus, the lithium surface should be protected by inorganic compounds prior to cycling to prevent it from undergoing side reactions with the electrolyte during cycling in the electrolyte.

Prediction of degradation in lithium−ion batteries is critical to ensure battery safety. In this study, we report for the first time that electrochemical impedance spectroscopy (EIS) predicts serious capacity fade in lithium−ion batteries, which results from charge−discharge cycling under overcharge conditions. A nickel cobalt aluminum oxide (NCA) lithium-ion cell shows a two-stage capacity fade in the overcharge condition with an upper cutoff voltage (UCV) of 4.4 V. The capacity gradually decreases as cycling progresses (first stage), and then decreases steeply in the later cycles (second stage). Such a two-stage capacity fade is not observed when cell cycling in the appropriate voltage range (UCV ≤ 4.2 V). In the first stage, the cell capacities cycled at UCVs of 4.2 V and 4.4 V are approximately identical, with an inductively coupled plasma atomic emission spectrometry analysis confirming overcharge-induced deposition of Ni and Co on the anode surface. EIS analysis is used to model these deposited metals as enhanced impedance signals that represent the charge transfer resistance and interfacial capacitance of the anode in the first stage. This allows the advance prediction of overcharge-induced serious capacity decay in lithium-ion batteries to prevent cell destruction.

The silicon-based composite prepared by electrodeposition exhibits outstanding electrochemical performances for several thousand cycles because the co-deposited oxygen and carbon could act as buffer materials to reduce internal stress during charge-discharge cycling. However, it is not easy to increase the loading amount of active materials due to low structural stability at a high passing charge over 15 C cm−2 for electrodeposition, leading the low areal capacity of Si–O–C composite as an anode. In this study, we propose a new way to enhance the structural stability of silicon-based anode by an electrochemical co-deposition technique using tin as supporting material, namely Sn–Si–O–C composite. The co-deposited tin has a whisker-shaped structure, and it prevents the exfoliation of activated material during electrodeposition. Besides, tin whisker can act as an electron pathway, resulting in improved electrochemical performance including high rate performance. The enhanced electrical conductivity is investigated by electrochemical impedance analysis. The improved electrochemical performance of Sn–Si–O–C composite indicates the high potential as an electrode material for high-performance lithium-ion batteries.

We report micrometre-thick porous Si–Cu anodes that are rapidly co-deposited on Cu current collectors in 1 min. This rapid deposition is realized by heating Si and Cu powders to ∼2000 °C and elevating their vapour pressures, while the porous and amorphous anode structure is realized by keeping the substrates at 100 °C. The films spontaneously form a 2–4.5-μm-thick composition gradient that changes from a Cu-rich region at the bottom to a Si-rich region at the top of the film, because of the higher vapour pressure for Cu than Si. A small addition of 5 wt% Cu to the Si source enhances the cycle performance of the film remarkably in a half-cell test, yielding a gravimetric capacity of 1250 mAh g film −1 , a volumetric capacity of 1956 mAh cm film −3 , and an areal capacity of 0.96 mAh cm anode −2 at the 100th cycle. However, excess addition of Cu causes partial Si crystallization in the films, which results in poorer cycle performance. While further improvement is needed, this rapid vapour deposition method yields Si–Cu films with compositional gradients on Cu current collectors in 1 min using inexpensive and safe Si and Cu powder sources, and is attractive for practical Si-based anode fabrication.

The electrodeposited Sn–O–C composite anode cycling with LiClO 4 delivered stable cycle performances showing discharge capacity of 473 mA h g of Sn −1 with 95% of coulombic efficiency at 100th cycle. However, the anode showed poor cycle performances with LiPF 6 delivering discharge capacity of 69 mA h g of Sn −1 at 100th cycle with 70% of coulombic efficiency. Electrochemical investigation performed by cyclic voltammetry and differential capacity plots revealed that the Sn–O–C composite cycling with LiPF 6 suffered from retarded phase transition reaction between Li and Sn during charge/discharge process. X-ray photoelectron spectroscopy declared the existence of fluorinated-Sn and LiF. Moreover, energy dispersive X-ray spectroscopy found increase in their amount with repeated cycles. The morphologies of the Sn–O–C composite cycled with LiPF 6 showed aggregated particles containing the chemical state of fluorinated-Sn and LiF on its surface. Furthermore, the significant pulverization and aggregation of the active material were observed from the Sn–O–C composite cycled by LiPF 6 rather than that of LiClO 4 , which was probably promoted by the generated HF strongly corroding metallic component.

In order to solve the problem of polysulfide dissolution into the electrolyte on sulfur-based cathodes, we propose a novel method of modifying the S cathode by coating it with a polypyrrole (PPy) film, which is prepared by oxidative electropolymerization using a solution consisting of, 1-methyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and pyrrole. The PPy film demonstrates a high Li+ transport number. The film also exhibits a superior ability to inhibit polysulfide dissolution into the electrolyte during the charge–discharge cycles. Furthermore, the charge–discharge properties of the coated cathode is evaluated using an electrolyte consisting of 1.0 M LiTFSI in a mixture of 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL), which is known to easily dissolve polysulfides. Because of the surface modification with the PPy film, the cathode exhibits excellent specific capacities of 823 and 354 mAh g−1 at C-rates of 0.1 and 1.0 C, respectively, with high coulombic efficiency. Thus, the strategy of coating the S cathode with PPy is successful in inhibiting the polysulfides dissolution even in electrolytes known to easily dissolve polysulfides, besides allowing high C-rate operation. Further, the modification of the S cathode allows the selection of a suitable electrolyte based on the anode, rather than being limited by the cathode.

Polyvinylpyrrolidone (PVP) is used with polyethylene oxide (PEO) as a mixed binder for mechanically milled Li 2 S. PVP demonstrates its advantage in terms of increasing the capacity of Li 2 S, but boosts the potential barrier at the beginning of the first charge. It is also revealed that PVP retards the charge-transfer kinetics of Li 2 S. In Li 2 S-C prepared by mechanical milling, carbon compensates for the electrochemical insulation of the PVP binder and improves the cycle stability. As a result, the Li 2 S-C-PVP electrode with 60 wt% Li 2 S content displays a low potential barrier at the onset of charge and a stable capacity of about 460 mAh g −1 at 0.1 C.