литий-ионные аккумуляторы

It is shown that an examination of reduced galvanostatic charge-discharge curves allows making preliminary conclusion on degradation mechanism upon cycling. If such degradation is due to loss of active material all normalized curves coincide. In the case of insulating films building up normalized curves are shifted along potential axis. Various structure changes result in qualitative change of curves shape.

Silicon electrodes with regular porous structure were prepared by the photoelectrochemical etching of single-crystal n-type silicon wafers, followed by the removal of the substrate. Electrodes with pores having circular and square section were studied. The porosity was increased via additional oxidation with the subsequent etching of oxide. The electrochemical characteristics of anodes were found to depend on porosity, electrodes with porosity 60-70% possessing maximal capacity for lithium reversible insertion. Electrodes thus prepared feature much higher capacity per area unit (up to 25 mA·h/cm2) than usual thin-film electrodes (about 1 mA·h/cm2).

On basis of analysis of literature data as well as of own experimental results we suggest some regularity for degradation of silicon electrodes upon cycling. It was shown that an electrode capacity Q at n-th cycle can be calculated from equation Q = Q₀ exp(kn+βn²/2), where Q₀ is initial capacity value, k и β are empiric constants.

Cycling tests of lithium-ion batteries in wide temperature and load ranges have been carried out. The existence of certain threshold discharge load corresponding abrupt decrease of discharge capacity was found.

Discharge behavior of lithium nano-titanate samples synthesized by solid-state methods from titania (anatase) and various lithium compounds has been studied. The shape of discharge curves was shown to change along with increasing current. This change was explained with due account for the model of heterogeneous lithium nano-titanate grain. It is found that the dependence of discharge capacity on current density does not obey to common Peukert equation but consists of two segments. In any cases the exponent in the Peukert equation does not exceed 0.2.