2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

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Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

A review on electrolyte additives for lithium-ion batteries

X-ray photoelectron spectroscopy and scanning electron microscopy were used to study electrode samples obtained from 18650-type lithium-ion cells subjected to accelerated calendar-life testing at temperatures ranging from 25 to 70 C and at states-of-charge from 40 to 80%. The cells contained LiNi{sub 0.8}Co{sub 0.2}O{sub 2}-based positive electrodes (cathodes), graphite-based negative electrodes (anodes), and a 1 M LiPF{sub 6} ethylene carbonate:diethyl carbonate (1:1) electrolyte. The results from electrochemically treated samples showed surface film formation on both electrodes. The positive electrode laminate surfaces contained a mixture of organic species that included polycarbonates, and LiF, Li{sub x}PF{sub y}-type and Li{sub x}PF{sub y}O{sub z}-type compounds. The same surface compounds were observed regardless of test temperature, test duration, and state-of-charge. On the negative electrode laminates lithium alkyl carbonates (ROCO{sub 2}Li) and Li{sub 2}CO{sub 3} were found in addition to the above-mentioned compounds. Decomposition of lithium alkyl carbonates to Li{sub 2}CO{sub 3} occurred on negative electrodes stored at elevated temperature. Initial depth-profiling results suggest that the surface layer thickness is greater on positive electrode samples from cells stored at high temperature than on samples from cells stored at room temperature. This observation is significant because positive electrode impedance, and more specifically, charge-transfer resistance at the electrode/electrolytemore » interface, has been shown to be the main contributor to impedance rise in these cells.« less

https://iopscience.iop.org/article/10.1149/1.1505636/pdf

Surface Characterization of Electrodes from High Power Lithium-Ion Batteries

The need for lighter, thinner, and smaller products makes lithium ion batteries popular power sources for applications such as mobile phones, laptop computers, digital cameras, electric vehicles, and hybrid electric vehicles. For high power applications, the development of high capacity and high voltage electrode materials is in progress. Battery performance and safety issues are also related to the properties of the electrolytes used. To improve the properties of the electrolytes, small amounts of other components, known as electrolyte additives, are incorporated. This paper reviews the recent progress in electrolyte additives used to improve performance and other properties, such as safety. This review classifies the additives based on their functions and their effects on specific electrode materials focusing on electrodes under current development. From anodes: carbonaceous electrodes, silicon, tin and Li4Ti5O12; from layered cathodes: LiCoO2, Li-rich and LiNiyMnyCo1−2yO2 (NMC); from spinel: LiMn2O4, and from olivine: LiFePO4 are selected. We believe that this approach will help readers easily identify and understand the additives suitable for their target materials.

Electrolyte additives for lithium ion battery electrodes: progress and perspectives

In situ hard X-ray absorption spectroscopy (XAS) at metal K-edges and soft XAS at O K-edge and metal L-edges have been carried out during the first charging process for the layered Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The metal K-edge XANES results show that the major charge compensation at the metal site during Li-ion deintercalation is achieved by the oxidation of Ni2+ ions, while the manganese ions and the cobalt ions remain mostly unchanged in the Mn4+ and Co3+ state. These conclusions are in good agreement with the results of the metal K-edge EXAFS data. Metal L-edge XAS results at different charge states in both the FY and PEY modes show that, unlike Mn and Co ions, Ni ions at the surface are oxidized to Ni3+ during charge, whereas Ni ions in the bulk are further oxidized to Ni4+ during charge. From the observation of O K-edge XAS results, we can conclude that a large portion of the charge compensation during Li-ion deintercalation is achieved in the oxygen site. By comparison to our earlier res...

/pdf/investigation-of-the-charge-compensation-mechanism-on-the-460be5jd4a.pdf

Investigation of the Charge Compensation Mechanism on the Electrochemically Li-Ion Deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 Electrode System by Combination of Soft and Hard X-ray Absorption Spectroscopy

The formation of a solid electrolyte interface (SEI) on LiNi 0 . 8 5 Co 0 . 1 5 O 2 cathodes from lithium-ion cells cycled at 40 and 70°C was observed and characterized using soft X-ray absorption spectroscopy (XAS). XAS measurements were made in the energy region between 500 and 950 eV, encompassing the Ni and Co L 3 - and L 2 -edges and at the K-edges of O and F. Measurements, obtained in the total electron yield mode, are surface sensitive, probing to a depth of ∼5 nm. XAS at the F K-edge demonstrates the presence of poly(vinylidene fluoride) (PVdF) in addition to LiF on the surface of cycled electrodes. The results indicate that the PVdF in the cycled electrodes is largely intact and that the LiF comes from decomposition of LiPF 6 from the electrolyte. XAS also suggests Fe contamination of cycled cathodes.

Formation of sei on cycled lithium-ion battery cathodes: soft x-ray absorption study

The electrochemical stability of the boron anion receptor, tris(pentafluorophenyl) borane (TPFPB), on a carbonaceous mesocarbon microbeads (MCMB) electrode and its compatibility with the passivated solid electrolyte interphase (SEI) layer on the carbon anode were investigated. Comparison of the irreversible capacity loss of the MCMB electrode during initial galvanostatic cycling using electrolyte with and without the TPFPB additive indicates excellent electrochemical stability of TPFPB on the carbonaceous electrode. Cyclic voltammetry studies show that the SEI layer on the surface of the carbon electrode can be formed through the decomposition of ethylene carbonate in the presence of TPFPB. Prolonged cycling test verifies the long-term stability of the SEI layer on carbon in the presence of the TPFPB additive. The SEI layer is not dissolved by TPFPB even after heat-treatment under conditions which dissolve LiF salt. This suggested a cross-linked structure for the SEI layer on carbon electrode. A Li-ion cell using an electrolyte containing TPFPB displays better cycling performance than a cell without TPFPB under the same conditions.

https://iopscience.iop.org/article/10.1149/1.1536475/pdf

The Compatibility of a Boron-Based Anion Receptor with the Carbon Anode in Lithium-Ion Batteries

Novel fluorinated boronate-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boronate-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boronate-based anion receptors include different fluorinated alkyl and aryl groups.

Xuehui Sun

Papers

Formation of sei on cycled lithium-ion battery cathodes: soft x-ray absorption study

The Compatibility of a Boron-Based Anion Receptor with the Carbon Anode in Lithium-Ion Batteries

Phenyl boron-based compounds as anion receptors for non-aqueous battery electrolytes