2020同步年報

Energy Science 055 Black Phosphorus Composites with Engineered Interfaces for High-Rate High-Capacity Lithium Storage Li ion battery is one of the most promising high energy density storage technologies for power- ing the green society. The prospect is bright, however, issues are still pending to be solved. Fig. 1 : Steps for the ion relocation between cathode and anode in a Li-ion battery. E nergy density and storage rates are the deciding fac- tors affecting widespread applications of a lithium-ion battery (LIB), for which the energy barriers and diffusion coefficient of Li + ions between the inter- and intra-component interfaces are critical issues. Among these interfaces, there are more than ten steps for Li + ion relocation ( Fig. 1 ) for performance optimization, including (1) Li + ion exchange between lattice sites and vacated sites in the active materi- al, (2) Li + ion relocation kinetics (barrier) between the active material and the solid electrolyte interface (SEI), (3) rate of Li + ion exchange (diffusion coefficient) in the solid electro- lyte interface, (4) Li + ion chelation by additives, (5) diffusion of chelated Li + ions (Li + -C) in the electrolyte, (6) Li + -C incor- poration in the separator, (7) ion relocation from Li + -C to carbon, (8) channel formation through formation of a Li + ion pillow between carbon layers, (9) Li + ion relocation in the channel, and (10) Li metal plating (if the rate of Li + ion relocation in the channel is less than that of step 7). The interfacial resistance of the SEI and a new class of configuration design are effective strategies to suppress the energy barrier (overpotential drop) and even to decrease the number of ion relocation interfaces, consequently making a significant breakthrough of the LIB performance. With these aforementioned understandings, Hengxing Ji (University of Science and Technology of China, China) and his international collaborators proposed a new interfacial engineering technology to enable high-rate and high- capacity lithium storage by coating covalently bonded black phosphorus (BP)-graphite particles with electrolyte-swollen polyaniline as nanoscaled composites. Such a design yields a stable solid–electrolyte interphase and inhibits the contin- uous growth of poorly conducting Li fluorides and carbon- ates to ensure efficient Li + transport ( Fig. 2 ) By collabo- rating with Cheng-Hao Chuang (Tamkang University) and Ting-Shan Chan (NSRRC), the corresponding mechanisms for Li + transport were deduced through use of X-ray absorp- tion spectral analysis at the P K-edge in situ at TLS 16A1 of the NSRRC. Accordingly, BP can deliver a gravimetric capac- ity 2596 mA·h g −1 (7, 8) at a 1C rate and is among the best three records for existing materials (note that the capacities for the first two materials are 4200 mA·h g −1 for Si and 3860 mA·h g −1 for Li metal) through a three-electron alloy- ing reaction with Li + ions. Most importantly, such a novel characteristic implements a rapid charge-discharge path for Li + storage with high columbic efficiency of the BP-graphite composite at the 2C and 4C rates without degradation, therefore shining light on widespread applications of elec- tronically powered public transport in the future. The Li-O 2 counterpart is a brand new design with fewer interfacial conjunctions in a LIB. It could be a promising solid-state prototype to resolve the pending controversy between high safety and high-rate considerations. However,