Composite electrolyte with self-inserted structure and all-trans F conformation provides fast Li^(+)transport for solid-state Li metal batteries

Solid-state Li metal battery has attracted increasing interests for its potentiallyhigh energy density and excellent safety assurance, which is a promising candidatefor next generation battery system. However, the low ionic conductivityand Li^(+) transport number of solid-state polymer electrolytes limit their practicalapplication. Herein, a composite polymer electrolyte with self-insertedstructure is proposed using the layered double hydroxides (LDHs) as dopant toachieve a fast Li^(+) transport channel in poly(vinylidene-co-trifluoroethylene) [P(VDF-TrFE)] based polymer electrolyte. In such a composite electrolyte, P(VDF-TrFE) polymer has an all-trans conformation, in which all fluorineatoms locate on one side of the polymer chain, providing fast Li^(+) transporthighways. Meanwhile, the LDH can immobilize the anions of Li salts based onthe electrostatic interactions, promoting the dissociation of Li salts, therebyenhancing the ionic conductivity (6.4 × 10^(-4) S cm^(-1)) and Li^(+) transferencenumber (0.76). The anion immobilization effect can realize uniform electricfield distribution at the anode surface and suppress the dendritic Li growth.Moreover, the hydrogen bonding interaction between LDH and polymerchains also endows the composite electrolyte with strong mechanical properties.Thus, at room temperature, the Li jj Li symmetric cells can be stablycycled over 1000 h at a current density of 0.2 mA cm^(-2), and the full cells withLiFePO_(4) cathode deliver a high capacity retention (>95%) after 200 cycles. This work offers a promising route to construct solid-state polymer electrolytes withfast Li^(+) transport.

V-doped Co-free Li-rich layered oxide with enhanced oxygen redox reversibility for excellent voltage stability and high initial Coulombic efficiency

Li-rich Mn-based oxides(LRMOs)hold great promise as next-generation cathode materials for high-energy Li-ion batteries because of their low cost and high capacity.Nevertheless,the practical application of LRMOs is impeded by their low initial Coulombic efficiency and rapid voltage decay.Herein,a V-doped layered-spinel coherent layer is constructed on the surface of a Co-free LRMO through a simple treatment with NH_(4)VO_(3).The layered-spinel coherent layer with 3D ion channels enhanced Li+diffusion efficiency,mitigates surface-inter-face reactions and suppresses irreversible oxygen release.Notably,V-doping significantly reduces the Bader charge of oxygen atoms,thereby impeding excessive oxidation of oxygen ions and further enhancing the stability of O-redox.The modified LRMO exhibites a remarkable initial Coulombic efficiency of 91.6%,signifi-cantly surpassing that of the original LRMO(74.4%).Furthermore,the treated sample showes an impressive capacity retention rate of 91.9%after 200 cycles,accompanied by a voltage decay of merely 0.47 mV per cycle.The proposed treatment approach is straightforward and significantly improves the initial Coulombic efficiency,voltage stability,and capacity stability of LRMO cathode materials,thus holding considerable promise for the development of high-energy Li-ion batteries.