Silicon (Si) has gained huge attention as an anode material for next-generation high-capacity lithium-ion batteries (LIBs). However, despite its overwhelming beneficial features, its large-scale commercialization is hampered due to unavoidable challenges such as colossal volume change during (de)­alloying, inherent low electronic and ionic conductivities, low Coulombic efficiency, unstable/dynamic solid electrolyte interphase (SEI), electrolyte drying and so forth. Among other strategies, the use of a fraction dose of chemical additives is hailed as the most effective, economic and scalable approach to realize Si-anode-based LIBs. Functional additives can modify the nature and chemical composition of the SEI, which in turn dictates the obtainable capacity, rate capability, Coulombic/energy efficiency, safety, and so forth of the battery system. Thus, we report a systematic and comparative investigation of various electrolyte additives, namely tetraethoxysilane (TEOS), (2-cyanoethyl)­triethoxysilane (TEOSCN), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and a blend of TEOSCN, VC, and FEC (i.e., VC/FEC/TEOSCN) using electrochemical analysis, X-ray photoelectron spectroscopy, density functional theory calculation, and differential scanning calorimetry. The ternary mixture (FEC/VC/TEOSCN) results in a thinner SEI layer consisting of high shear modulus SEI-building species (mainly LiF). It also provides much improved thermal stability amid all tested additives, showing its potentiality to enable high capacity and safer Si-based anode LIBs. Thus, nitrile-functionalized silanes are highly promising electrolyte additives to boost the electrochemical performance and safety-induced risks of Si-based anode LIBs, emanating from the formation of a robust SEI layer.

PEO-based solid polymer electrolytes typically show limited capability for the suppression of Li metal dendrites, which is mainly attributed to their low mechanical strength. To tackle this issue, we improved the mechanical strength of a ternary solid polymer electrolyte (TSPE: PEO-LiTFSI-Pyr 14 TFSI) by integrating Celgard 2500 separator as a high modulus domain. The Celgard-reinforced TSPE (CgTSPE) presents a significantly higher elastic modulus (223 MPa) than TSPE (0.2 MPa) at 60°C, which in result leads to more lithium anode utilization. Specifically, the Columbic efficiency of Li electrodeposition/dissolution during cycling in Li|CgTSPE|Cu cells (≈90%) is distinctly higher than in Li|TSPE|Cu (≈30%). Furthermore, the cycling of Li||Li symmetric cells with CgTSPE displays an improved cycling stability, due to the presence of Celgard, in which high surface area lithium (HSAL), e.g., dendrite formation is suppressed. Operando electrochemical dilatometry (ECD) analysis as well as post mortem surface analysis with SEM reveal the formation of "dead lithium" and cavities under an areal capacity utilization of 5 mAh/cm 2 . It is also suggested by the cycling behavior of the Li||Li cell with high areal capacity utilization that lithium surface treatment is required to completely eliminate the formation of "dead lithium" and of cavities.

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Nail penetration tests under adiabatic conditions are proposed as a new safety test method to simulate a short circuit caused by intrusion in the worst case scenario, i.e., adiabatic conditions. The behaviors of commercially available 18650 type lithium-ion cells with two different cell chemistries, LiNi 0.33 Co 0.33 Mn 0.33 O 2 -LiCoO 2 blend (NCM-LCO blend) vs. graphite and LiFePO 4 (LFP) vs. graphite, were investigated at different states of charge (SoC). The results show a small standard deviation for the temperature and pressure measurements from five identical experiments. The detailed examination of the nail penetration experiments reveals differences in the safety properties of the cathode materials (LFP vs. NCM-LCO), separator types (PP PE PP trilayer vs. PE single layer) and electrode designs (high power vs. high energy). For both cell types, the observed cooling effect at high energy contents could be linked to an increased gas production due to the loss of electrolyte.

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The urgent need for improving the energy density of aqueous lithium ion batteries (ALIBs) can be addressed by the implementation of advanced electrode materials and electrolytes. The utilization of layered...

The urgent need for higher energy density of aqueous Li-ion batteries (ALBs) cannot only be satisfied by electrolyte modifications, the utilization of layered oxide cathodes is another efficient strategy, and particularly Li[NixCoyMn1-x-y]O2 (NCM) materials are of high interest due to their high specific capacities. Concerning the H+-Li+ exchange side reaction of layered cathode in water solution, however, whether proton contamination degrades NCM-type cathodes in highly-concentrated aqueous electrolyte is an unclear but meaningful point. In this work, the underlying mechanisms responsible for degradation of NCM622 | aqueous/non-aqueous hybrid electrolyte |TiO2/LiTi2(PO4)3 (P/N=1.2:1) full-cells are explored by comprehensive studies involving in the evolution of electrochemical impendence and lattice structure changes after cycling within different operating voltage ranges. It is found that proton co-intercalation into the layered structure still takes place in high concentration aqueous/non-aqueous hybrid electrolytes, and the NCM622 cathode quickly shows degradation after being charged to higher cut-off voltage owing to severe protonation. The introduced proton can increase the diffusion barrier for Li+ ions, which in turn hinders lithiation of the de-lithiated cathode.