wileyonlinelibrary.comAdv. Energy Mater. 2011, 1, [58][59][60][61][62] Extensive studies on intercalation electrodes have enabled rapid development of lithium-ion batteries for electronic applications. However, limited cycle life and moderate rate-capability as well as the high-cost of electrode materials still restrict penetration of Li-ion cells for vehicular applications. [ 1 ] LiCoO 2 , the most commonly employed cathode in portable electronics with a capacity of ~135 mAh g − 1 , is expensive, toxic and unstable at higher voltages ( > 4.3 V). [2][3][4] Recently, Ni and Mn substituted compounds (LiNi y Mn y Co 1-2y O 2 (0 < y ≤ 0.5)) have been explored. [ 2 , 5-8 ] Unfortunately, the instability of de-lithiated Li x NiO 2 and LiMnO 2 limits their usage as Li-ion cathodes. [9][10][11] Although, the LiNi y Mn y Co 1-2y O 2 (0 < y ≤ 0.5) compounds show better thermal stability in organic electrolytes, [ 12 , 13 ] the electronic conductivity and structural stability are lower than that of LiCoO 2 , thereby negatively affecting rate capability and lifetime, respectively. Different compounds with variations in y (LiNi y Mn y Co 1-2y O 2 ) including the one discussed here have been studied, but it has still not been possible to demonstrate stable high rates with conventional electrodes. [ 14 , 15 ] Recent research in the Whittingham group has shown that LiNi y Mn y Co 1-2y O 2 (y = 0.4, 0.45) compounds have higher capacities than other compositions but still exhibit low rate-capability. [ 16 ] Many efforts to enhance the conductivity of layered structures that improves the rate performance of Ni and Mn substituted compounds have been undertaken. Carbon coatings have been successfully employed to improve electronic conductivity. [17][18][19] The use of nanoscale materials is also considered an effective way to ameliorate rate performance due to shorter lithium diffusion paths. [ 20 , 21 ] But, the large surface area of nanomaterials can cause undesirable side reactions that ultimately impair cycling performance. [ 22 ] Surface coatings with stable chemicals such as Al 2 O 3 and ZrO 2 have been employed to protect the surface resulting in a longer cycle-life. [ 2 , 23 ] However, the electronic conductivity may be reduced if the coating is an insulating material. [ 24 ] In our previous work we demonstrated that single-walled carbon nanotubes (SWNTs) could be employed as a fl exible net enabling reversible cycling for a high volume expansion materials. [ 25 ] In this work the cathode material does not undergo volume expansion but suffers from poor electrical conductivity and surface over-charge/over-discharge causing capacity fade, especially at high rate. We now demonstrate that the SWNTs can improve both conductivity and also stabilize the surface at an exceptionally high rate of 10C (charge/discharge in 6 min). Specifi cally, by constructing an LiNi 0.4 Mn 0.4 Co 0.2 O 2 cathode (NMCSWNT) with 5 wt.% SWNTs, the cathode is shown to have a capacity of ˜130 mAh g − 1 at 5C and nearly 120 mAh g − 1 at 10C, both for...