Merck KGaA developed LiPF 3 (CF 2 CF 3 ) 3 , ͑LiFAP͒ as a new electrolyte that can replace the commonly used LiPF 6 in Li-ion batteries. Vinylene carbonate and Li salicylato borate ͑Merck's AD25͒ were studied as additives for LiFAP solutions in mixtures of ethylene, dimethyl, and diethyl carbonates with composite graphite and LiMn 2 O 4 electrodes. The tools for this study included voltammetry ͑fast and slow scan rates͒, chronopotentiometry, impedance spectroscopy, electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that LiFAP solutions containing VC were superior for both graphite and LiMn 2 O 4 ͑spinel͒ electrodes. The effect of additives on the electrodes' performance can be clearly attributed to their impact on the surface chemistry of these electrodes.The increasing demand of power sources for portable equipment and electric vehicles has intensified efforts to develop rechargeable lithium batteries with high power density and rapid rechargeability. The most common Li-ion batteries comprise lithiated graphite anodes, LiCoO 2 ͑composite͒ cathodes, and electrolyte solutions based on LiPF 6 salt in organic carbonate solvents. 1 In general, both the solvent molecules and the PF 6 Ϫ anions are reduced on the Li-C electrodes to form surface films comprising ROCO 2 Li, ROLi, and Li 2 CO 3 , species containing Li-C bonds, polymeric species ͑e.g., polycarbonate, polyethylene͒, LiF, Li x PF y , and Li x POF y species. 2 These films passivate the Li-C electrode and lead to their apparent ͑kinetically controlled͒ stability in solutions. Also, surface films are formed on LiMO 2 cathodes in these solutions (M ϭ V, Co, Mn, etc͒. 3 The performance of the cathodes is also largely influenced by surface phenomena. 4 LiPF 6 was chosen to be the commercially used electrolyte for Li-ion batteries only because other available salts are worse ͑for example: LiClO 4 is explosive, and LiAsF 6 is excluded due to the arsenic͒. LiPF 6 itself always brings with it HF contamination, which is detrimental to the performance of both negative and positive electrodes. 5 There is a pronounced difference in the surface chemistry of the negative and the positive electrodes in Li-ion batteries. In the case of the Li-C electrodes there is a constant driving force for the reduction of solution species, and hence, their passivation phenomena are driven by electrochemical ͑cathodic͒ reactions. In the case of cathodes, there is no major electrochemical reactivity of the solutions at the usual maximal charging potential of the cathodes (E Ͻ 4.2-4.3 V vs. Li/Li ϩ ). The major possible surface reactions of the cathodes are driven by chemical properties. For instance, HF reacts with the LiMO 2 cathode materials to form surface LiF, and some of the cathode materials, e.g., LiNiO 2 , are nucleophilic and attack the electrolytic alkyl carbonate molecules, thus forming ϪOCO 2 Li surface groups and/or inducing polymeric species such as polycarbonates. 6 It should be noted that the capacity fading found...