Multifunctional cellular architecture of sulfur doped graphene paves the way for high performance flexible energy device application.

there are only a few reports on 2D LiFePO 4 materials with outstanding high-rate performance and hybrid battery and supercapacitor behavior. [9,[13][14][15] This is due to the fact that transition metals in cathode materials would undergo oxidation to higher valence states on the removal of lithium or other cations, [16] leading to large compositional changes and the consequent phase changes. Therefore, cathode materials require high structural stability to provide a high specific capacity at high charge and discharge rates, as well as suitable morphology and particle size. Nowadays, the challenge is to develop a versatile, scalable, highly efficient process to synthesize 2D cathode nanosheets, which could maintain their stable crystal structure and uniform microstructure over the long run.The current state-of-the-art cathode materials for Li-ion batteries mainly have three different type of structures, including layered (LiCoO 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNiCoAlO 2 ), spinel (LiMn 2 O 4 ), and olivine-type (LiFePO 4 ) structures. (Please see Figure S1, Supporting Information.) Moreover, the diffusion direction of lithium in LiCoO 2 is octahedral site-tetrahedral site-octahedral site in layers, while that in LiMn 2 O 4 is tetrahedral siteoctahedral site-tetrahedral site with 3D channels, and the motion of lithium ions in LiFePO 4 occurs along 1D channels via nonlinear trajectory in the olivine crystal structure. [17] These different structures certainly will increase the difficulty of the synthesis of 2D cathode nanosheets. Thus, it is a challenge to adopt a general process to synthesize their 2D nanosheets from the corresponding particles with different crystal structures. In addition, the storage mechanisms of 2D layered lithium transition metal oxides or spinel LiMn 2 O 4 nanosheets still need investigation.Herein, we used an effective, easily scaled-up, and general synthetic process for the preparation of few-layered positive electrode nanosheets, which include layered LiCoO 2 , olivinetype LiFePO 4 , and spinel-type LiMn 2 O 4 . These prepared nanosheets showed highly oriented facets, which will have benefits for the lithium ion de-insertion/insertion during the charging/discharging process, respectively, thereby delivering high-energy densities and excellent rate capabilities. Also, the structural evolution of 2D cathode materials during galvanostatic charge-discharge was captured using time-resolved in situ synchrotron X-ray powder diffraction. The transport channels of 2D cathode materials would be opened up to different The most promising cathode materials, including LiCoO 2 (layered), LiMn 2 O 4 (spinel), and LiFePO 4 (olivine), have been the focus of intense research to develop rechargeable lithium-ion batteries (LIBs) for portable electronic devices. Sluggish lithium diffusion, however, and unsatisfactory long-term cycling performance still limit the development of present LIBs for several applications, such as plug-in/hybrid electric vehicles. Motivated by the success of graphene and novel 2D m...

A room-temperature all-solid-state rechargeable battery cell containing a tandem electrolyte consisting of a Li-glass electrolyte in contact with a lithium anode and a plasticizer in contact with a conventional, low cost oxide host cathode was charged to 5 V versus lithium with a charge/discharge cycle life of over 23,000 cycles at a rate of 153 mA·g of active material. A larger positive electrode cell with 329 cycles had a capacity of 585 mAh·g at a cutoff of 2.5 V and a current of 23 mA·g of the active material; the capacity rose with cycle number over the 329 cycles tested during 13 consecutive months. Another cell had a discharge voltage from 4.5 to 3.7 V over 316 cycles at a rate of 46 mA·g of active material. Both the Li-glass electrolyte and the plasticizer contain electric dipoles that respond to the internal electric fields generated during charge by a redistribution of mobile cations in the glass and by extraction of Li from the active cathode host particles. The electric dipoles remain oriented during discharge to retain an internal electric field after a discharge. The plasticizer accommodates to the volume changes in the active cathode particles during charge/discharge cycling and retains during charge the Li extracted from the cathode particles at the plasticizer/cathode-particle interface; return of these Li to the active cathode particles during discharge only involves a displacement back across the plasticizer/cathode interface and transport within the cathode particle. A slow motion at room temperature of the electric dipoles in the Li-glass electrolyte increases with time the electric field across the EDLC of the anode/Li-glass interface to where Li from the glass electrolyte is plated on the anode without being replenished from the cathode, which charges the Li-glass electrolyte negative and consequently the glass side of the Li-glass/plasticizer EDLC. Stripping back the Li to the Li-glass during discharge is enhanced by the negative charge in the Li-glass. Since the Li-glass is not reduced on contact with metallic lithium, no passivating interface layer contributes to a capacity fade; instead, the discharge capacity increases with cycle number as a result of dipole polarization in the Li-glass electrolyte leading to a capacity increase of the Li-glass/plasticizer EDLC. The storage of electric power by both faradaic electrochemical extraction/insertion of Li in the cathode and electrostatic stored energy in the EDLCs provides a safe and fast charge and discharge with a long cycle life and a greater capacity than can be provided by the cathode host extraction/insertion reaction. The cell can be charged to a high voltage versus a lithium anode because of the added charge of the EDLCs.

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