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Abstract: A polytriphenylamine (PTPAn)-modified separator was prepared simply by impregnating triphenylamine monomers into a commercial Celgard separator and in situ polymerizing the monomers into electroactive phase by oxidant ozone. This type of electroactive separator can transform from an insulating state to a conductive state at overcharged voltage of ∼3.7V (vs. Li+/Li) and act as a self-actuating potential-switchable separator for overcharge protection of LiFePO4/C Li-ion batteries. The experimental results demonstrated that this electroactive separator can reversibly control the cell''s voltage at the safe value less than 4.15V at high rate overcharge of 2C current without obvious negative impact on the normal charge–discharge performances of the commercial LiFePO4/C batteries even at prolonged overcharge cycling, showing a potential application in 3.6V-class lithium-ion batteries. [Copyright &y& Elsevier]

Abstract: A voltage-sensitive separator is prepared simply by impregnating electroactive poly(3-decylthiophene) (P3DT) polymer into a commercial porous separator and tested for a self-actuating control of overcharge voltage of LiFePO4/C lithium-ion batteries. The experimental results demonstrate that this type of separator can be reversibly p-doped and dedoped to maintain the cell''s voltage at a safe value of ≤4V even at high rate overcharge of 3C current, effectively protecting the batteries from voltage runaway. Since this P3DT-modified separator has no obvious negative impact on the normal charge–discharge performance of the batteries, it may be adopted for practical application in commercial lithium ion batteries. [Copyright &y& Elsevier]

Abstract: A novel compound, tri-(4-methoxythphenyl) phosphate, was synthesized and investigated as a safety electrolyte additive for lithium-ion batteries. It was found that this additive could lower the flammability of the electrolyte, and thereby enhance the thermal stability of the Li-ion battery. Moreover, this molecule can also be polymerized at 4.35V (vs. Li/Li+) to form a conducting polymer, which can protect the batteries from voltage runaway at overcharge by internal bypassing the overcharging current in the batteries. Thus, it is possible to use this electrolyte additive to provide both overcharge protection and flame retardancy for lithium-ion batteries without much influence on the battery performance. [Copyright &y& Elsevier]

Abstract: A polymerizable monomer, diphenylamine (DPAn), is reported to act as a safety electrolyte additive for overcharge protection of 3.6V-class lithium ion batteries. The experimental results demonstrated that the DPAn monomer could be electro-polymerized to form a conductive polymer bridging between the cathode and anode of the battery, and to produce an internal current bypass to prevent the batteries from voltage runaway during overcharge. The charge–discharge tests of practical LiFePO4/C batteries indicated that the DPAn additive could clamp the cell''s voltage at the safe value less than 3.7V even at the high rate overcharge of 3C current, meanwhile, this monomer molecule has no significant impact on the charge–discharge performance of the batteries at normal charge–discharge condition. [Copyright &y& Elsevier]

Abstract: A compound 4-tertbutyl-1,2-dimethoxybenzene (TDB) was synthesized and tested as a redox shuttle for overcharge protection of Li–LiFePO4 batteries. This isomer of tertbutyl-substituted dimethoxybenzene is miscible with the organic polar electrolytes and provides a solution for the poor solubility of ditertbutyl-substituted 1,4-dimethoxybenzenes as a redox shuttle additive. The experimental results demonstrated that the shuttle molecules added in the electrolyte cannot only provide feasible overcharge protection, but also have indiscernible detrimental influences on the charge–discharge behaviors of Li–LiFePO4 cells, showing a great prospect for practical applications in commercial rechargeable lithium batteries. [Copyright &y& Elsevier]

Abstract: An electroactive polytriphenylamine (PTPAn) was synthesized and used as separator material for providing a self-activating overcharge protection of rechargeable lithium batteries. The experimental results from the Li–LiFePO4 cells demonstrated that the electroactive separator could transform from an electronically isolating state to a conductive state at overcharge, producing an resistive internal short circuit to maintain the cell''s voltage at the safety value of ∼3.75V. In addition, the electroactive PTPAn separator works reversibly and has no negative influences on the normal charge–discharge behaviors of the Li–LiFePO4 cells. [Copyright &y& Elsevier]

Abstract: A composite electroactive polymer membrane capable of providing a reversible self-activating current shunt for overcharge protection of lithium ion batteries is described. The membrane is composed of p-polyphenyl (PPP) and polyaniline (PAn), and can be p-doped at high oxidation potentials into conductive phase and de-doped at normal operating voltages into an electronically isolating separator, functioning as a potential-sensitive switch for controlling the battery voltage at charging. The experimental results from the laboratory Li–LiMn2O4 cells demonstrate that this composite membrane can reversibly control the battery voltage at required value at prolonged overcharge and has no negative impact on the battery performances at normal charge–discharge conditions. [Copyright &y& Elsevier]