An alternating stack (SG/GN) consisting of SnO₂-functionalized graphene oxide (SG) and amine-functionalized GO (GN) is prepared in solution. The thermally reduced SG/GN (r(SG/GN)) with decreased micro-mesopores and completely eliminated macropores, results in a high reversible capacity and excellent capacity retention (872 mA h g⁻¹ after 200 cycles at 100 mA g⁻¹) when compared to a composite without GN.

Self-charging power packs (SPPs), integrating both a solar cell and energy storage capacitor (EC) into a single device, are very promising energy systems due to their multiple functions of energy harvesting and storage.

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Graphene was used to form efficient conducting networks and to suppress the formation of a solid-electrolyte interface layer, in a sandwiched composite with LiNi0.5Mn1.5O4 (LNMO), which resulted in an improvement in rate capability and coulombic efficiency, respectively. The interaction between the LNMO particles and the residual oxygen functionalities on the basal plane of graphene in solution spontaneously produced LNMO particles that were sandwiched by the graphene. This configuration provided LNMO with less polarization due to higher electronic conductivity, which contributed to an increased rate capability. The graphene-sandwiched LNMO also enhanced a coulombic efficiency due to the suppression of continuous electrolyte decomposition, which eventually resulted in improved capacity retention. Unlike this graphene-sandwiched LNMO, a simple mixture of LNMO with graphene did not show noticeable improvements in rate capability due to a lack of efficient conducting network. A LiMn2O4/graphene composite prepared using the same procedure showed no improvement in coulombic efficiency and, thus, capacity retention was similar to graphene-free LiMn2O4, indicating that the graphene-sandwiching is an effective strategy for high-voltage cathode materials.

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Gadolinium-doped LiGd x Mn 2−x O 4 was synthesized by a sol-gel method and applied as cathode material in Li ion batteries. Gddoping significantly changed the unit cell parameter and atomic arrangement. With an increase of x, a cell dimension contracts from 8.2419(2) to 8.2375(8) (x = 0.02), 8.2295(3) (x = 0.04), and 8.2120(6) Å (x = 0.08), with concomitant changes in bond length. The LiO 4 tetrahedron expands to facilitate a fast electrochemical process and the MnO 6 octahedron shrinks to provide structural integrity. The former contributes to a better high-rate performance and the latter leads to a variation in the cell dimensions during charge-discharge cycles that is less than that found in LiMn 2 O 4 (structure-stabilization). The strong octahedral framework eventually results in minimized contraction of the unit cell after repeated cycles and in good capacity retention. A less capacity fading of LiGd 0.02 Mn 2.98 O 4 can be correlated to a smaller dimensional variation between charged and discharged states (LiMn 2 O 4 : 8.1366 and 8.0460 Å (two phases, charged) and 8.2419 Å (discharged) vs. LiGd 0.02 Mn 2.98 O 4 : 8.1472 Å (single phase, charged) to 8.2375 Å (discharged)) and, thus, the less unit cell contraction for LiGd 0.02 Mn 2.98 O 4 after repeated cycling (LiMn 2 O 4 : 8.2419 Å to 8.218 Å vs. LiGd 0.02 Mn 2.98 O 4 : 8.2375 Å to 8.229 Å).

Nanocomposites consisting of Sn nanoparticles and graphene oxide (GO) were electrophoretically deposited onto Cu current collectors that was used for anodes in Li ion batteries (LIBs). In order to optimize the electrochemical performance of nanocomposites as an anode material by controlling the oxygen functionality, the GO was subjected to O 3 treatment prior to electrophoretic deposition (EPD). During thermal reduction of the GO in the nanocomposites, the Sn nanoparticles were reduced in size, along with the formation of SnO and/ or SnO 2 at a small fraction, relying on the oxygen functionalities of the GO. The variation in the duration of time for the O 3 irradiation resulted in a small change in total oxygen content, but in a significantly different fraction of each functional group in the GO, which influenced the Sn nanoparticle size and the amount of SnO (and/or SnO 2 ). As a result, the EPD films prepared with the GO that possessed the least amount of carboxylic groups (made by treating GO in an O 3 environment for 3 h) showed the best performance, when compared with the nanocomposites composed of untreated GO or GO that was O 3 -treated for a duration of less than 3 h.