Promoting uniform lithium deposition with Janus gel polymer electrolytes enabling stable lithium metal batteries

Lithium metal batteries (LMBs) are desirable candidates owing to their highenergyadvantage for next-generation batteries. However, the practical applicationof LMBs continues to be constrained by thorny safety issues with the formationand growth of Li dendrites. Herein, the ZIF-67 MOFs are in situcoupled onto a single face of 3D porous nanofiber to fabricate an asymmetricJanus membrane, harnessing their anion adsorption capabilities to promotethe uniform deposition of Li ions. In addition, the poly(ethylene glycol)diacrylate and trifluoromethyl methacrylate are introduced into nanofiber skeletonto form Janus@GPE, which preferentially reacts with Li metal to form aLiF-rich stable SEI layer to inhibit Li dendrite growth. Importantly, the synergisticeffect of the MOFs and stable solid electrolyte interphase (SEI) layerresults in superior cycling performance, achieving a remarkable 2500 h cyclingat 1 mA cm^(-2) in the Li/Janus@GPE/Li configuration. In addition, theJanus@GPE electrolyte has a certain flame retardant, which can selfextinguishwithin 3 s, improving the safety performance of the batteries. Consequently,the Li/Janus@GPE/LFP flexible pouch cell exhibits favorablecycling stability (the capacity retention rate of 45 cycles is 91.8% at 0.1 C). Thiswork provides new insights and strategies to improve the safety and practicalutility of LMBs.

A nano fiber–gel composite electrolyte with high Li^(+) transference number for application in quasi-solid batteries

As their Liþtransference number(tLiþ),ionic conductivity,and safety are all high,polymer electrolytes play a vital role in overcoming uncontrollable lithium dendrites and low energy density in Li metal batteries(LMBs).We therefore synthesized a three-dimensional(3D)semi-interpenetrating network-based single-ion-conducting fiber–gel composite polymer electrolyte(FGCPE)via an electrospinning,initiation,and in situ polymerization method.The FGCPE provides high ionic conductivity(1.36 mS cm^(-1)),high t_(Li+)(0.92),and a high electrochemical stability window(up to 4.84 V).More importantly,the aromatic heterocyclic structure of the biphenyl in the nanofiber membrane promotes the carbonization of the system(the limiting oxygen index value of the nanofiber membrane reaches 41%),giving it certain flame-retardant properties and solving the source-material safety issue.Due to the in situ method,the observable physical interface between electrodes and electrolytes is virtually eliminated,yielding a compact whole that facilitates rapid kinetic reactions in the cell.More excitingly,the LFP/FGCPE/Li cell displays outstanding cycling stability,with a capacity retention of 91.6%for 500 cycles even at 10C.We also test the FGCPE in high-voltage NMC532/FGCPE/Li cells and pouch cells.This newly designed FGCPE exhibits superior potential and feasibility for promoting the development of LMBs with high energy density and safety.