Self-actuating protection mechanisms for safer lithium-ion batteries

Safety issue is still a problem nowadays for the large-scale application of lithium-ion batteries(LIBs)in electric vehicles and energy storage stations.The unsafe behaviors of LIBs arise from the thermal run-away,which is intrinsically triggered by the overcharging and overheating.To improve the safety of LIBs,various protection strategies based on self-actuating reaction control mechanisms(SRCMs)have been proposed,including redox shuttle,polymerizable monomer additive,potential-sensitive separator,thermal shutdown separator,positive-temperature-coefficient electrode,thermally polymerizable addi-tive,and reversible thermal phase transition electrolyte.As build-in protection mechanisms,these meth-ods can sensitively detect either the temperature change inside battery or the potential change of the electrode,and spontaneously shut down the electrode reaction at risky conditions,thus preventing the battery from going into thermal runaway.Given their advantages in enhancing the intrinsic safety of LIBs,this paper overviews the research progresses of SRCMs after a brief introduction of thermal runaway mechanism and limitations of conventional thermal runaway mitigating measures.More importantly,the current states and issues,key challenges,and future developing trends of SRCTs are also discussed and outlined from the viewpoint of practical application,aiming at providing insights and guidance for developing more effective SRCMs for LIBs.

Enabling a stable and dendrite-suppressed Zn anode via facile surface roughness engineering

The safety and cycle lifespan of zinc metal-based aqueous batteries are greatly restricted by zinc anode.The poor cycling performance of zinc metal anode is often considered to be impacted by the dendrite growth,surface passivation,zinc metal corrosion and hydrogen evolution reaction,while surface roughness is a matter that has often been ignored in past studies.Herein,a roughness gradient is constructed on the zinc anode surface by a simple grinding and pasting method.It has been found the modified zinc anodes with lower surface roughness exhibit the smaller zinc deposition overpotential and longer cycle life.Further,in situ optical microscopy photographs indicate that the zinc anode with an optimized roughness enables more uniform distribution of zinc precipitation and corrosion sites,which will facilitate a stable cycling performance of aqueous zinc ion batteries.The Zn anode dendrite-suppressing mechanism via surface roughness engineering was revealed through finite element computational simulation.These results emphasize the effectiveness of roughness engineering for tuning the surface physics of Zn anode and provide a facile strategy to develop better and safer aqueous zinc ion batteries.