Chip Design of Li-Ion Battery Charger Operating in Constant-Current/Constant-Voltage Modes

A design for a Li-ion battery charger IC that can operate in a constant current-constant voltage （CC- CV） charge mode is proposed. In the CC-CV charge mode,the charger IC provides a constant charging current at the beginning, and then the charging current begins to decrease before the battery voltage reaches its final value. After the battery voltage reaches its final value and remains constant,the charging current is further reduced. This approach prevents charging the battery with full current near its saturated voltage,which can cause heating. The novel design of the core of the charger IC realizes the proposed CC-CV charge mode. The chip was implemented in a CSMC 0.6μm CMOS mixed signal process. The experimental results verify the realization of the proposed CC- CV charge mode. The voltage of the battery after charging is 4. 1833V.

Model based SOC estimation for high-power Li-ion battery packs used on FCHVs

A model based method which recruited the extended Kalman filter （EKF） to estimate the full state of charge （SOC） of Li-ion battery was proposed. The underlying dynamic behavior of the cell pack was described based on an equivalent circuit comprising of two capacitors and three resistors. Measurements in two tests were applied to compare the SOC estimated by model based EKF estimation with the SOC calculated by coulomb counting. Results have shown that the proposed method is able to perform a good estimation of the SOC of battery packs. Moreover, a corresponding battery management systems （BMS） including software and hardware based on this method was designed.

Electrochemical impedance spectra of V_2O_5 xerogel films with intercalation of lithium ion

Vanadium pentoxide xerogel films used for lithium rechargeable batteries were prepared from crystalline c-V2O5 by melt quenching method,then the electrochemical process of lithium intercalation into vanadium pentoxide xerogel films was simulated with an equivalent circuit model, which was derived from the mechanism of electrode reactions. Measured electrochemical impedance spectra at various electrode potentials were analyzed by using the complex non-linear least-squares fitting method. The results show that impedance spectra consist of 2 high-to- medium frequency depressed arcs and a low frequency straight line. The high frequency arc is attributed to the absorption reaction of lithium ions into the oxide film, the medium frequency arc is attributed to the charge transfer reaction at the vanadium oxide/electrolyte interface and the low frequency is characterized by a straight line with a phase angle of 45° corresponding to the diffusion of lithium ion through vanadium oxide phase. The experimental and calculated results are compared and discussed focusing on the electrochemical performance and the state of charge of the electrode. Moreover, the high consistence of the fitted values of the model to the experimental data indicates that this mathematical model does give a satisfying description of the intercalation process of vanadium pentoxide xerogel films.

Electrochemical Performance and ex situ Analysis of ZnMn2O4 Nanowires as Anode Materials for Lithium Rechargeable Batteries

One-dimensional ZnMn2O4 nanowires have been prepared and investigated as anode materials in Li rechargeable batteries. The highly crystalline ZnMn2O4 nanowires about 15 nm in width and 500 nm in length showed a high specific capacity of about 650 mAh.g-1 at a current rate of 100 mA.g-1 after 40 cycles. They also exhibited high power capability at elevated current rates, i.e., 450 and 350 mAh.g 1 at current rates of 500 and 1000 mA.g 1, respectively. Formation of Mn3O4 and ZnO phases was identified by ex situ X-ray diffraction （XRD） and transmission electron microscopy （TEM） studies after the initial discharge-charge cycle, which indicates that the ZnMn2O4 phase was converted to a nanocomposite of Mn3O4 and ZnO phases immediately after the electrochemical conversion reaction.

Controlled Ag-driven superior rate-capability of Li4Ti5O12 anodes for lithium rechargeable batteries

The morphology and electronic structure of a Li4Ti5012 anode are known to determine its electrical and electrochemical properties in lithium rechargeable batteries. Ag-Li4Ti5012 nanofibers have been rationally designed and synthesized by an electrospinning technique to meet the requirements of one-dimensional （1D） morphology and superior electrical conductivity. Herein, we have found that the 1D Ag-Li4Ti5012 nanofibers show enhanced specific capacity, rate capability, and cycling stability compared to bare Li4Ti5012 nanofibers, due to the Ag nanoparticles （〈5 nm）, which are mainly distributed at interfaces between Li4Ti5O12 primary particles. This structural morphology gives rise to 20% higher rate capability than bare Li4Ti5O12 nanofibers by facilitating the charge transfer kinetics. Our findings provide an effective way to improve the electrochemical performance of Li4Ti5O12 anodes for lithium rechargeable batteries.

1,3-Dimethyl-2-imidazolidinone: an ideal electrolyte solvent for high-performance Li–O;battery with pretreated Li anode

Electrolytes are widely considered as a key component in Li–O;batteries (LOBs) because they greatly affect the discharge-charge reaction kinetics and reversibility.Herein,we report that 1,3-dimethyl-2-imidazolidinone (DMI) is an excellent electrolyte solvent for LOBs.Comparing with conventional ether and sulfone based electrolytes,it has higher Li_(2)O_(2)and Li_(2)CO_(3)solubility,which on the one hand depresses cathode passivation during discharge,and on the other hand promotes the liquid-phase redox shuttling during charge,and consequently lowers the overpotential and improves the cyclability of the battery.However,despite the many advantages at the cathode side,DMI is not stable with bare Li anode.Thus,we have developed a pretreatment method to grow a protective artificial solid-state electrolyte interface(SEI) to prevent the unfavorable side-reactions on Li.The SEI film was formed via the reaction between fluorine-rich organic reagents and Li metal.It is composed of highly Li^(+)-conducting Li_(x)BO_(y),LiF,Li_(x)NO_(y),Li_(3)N particles and some organic compounds,in which Li_(x)BO_(y)serves as a binder to enhance its mechanical strength.With the protective SEI,the coulombic efficiency of Li plating/stripping in DMI electrolyte increased from 20%to 98.5%and the fixed capacity cycle life of the assembled LOB was elongated to205 rounds,which was almost fivefold of the cycle life in dimethyl sulfoxide (DMSO) or tetraglyme(TEGDME) based electrolytes.Our work demonstrates that molecular polarity and ionic solvation structure are the primary issues to be considered when designing high performance Li–O;battery electrolytes,and cross-linked artificial SEI is effective in improving the anodic stability.