Lithium-Ion Rechargeable Cells
The history of lithium-ion rechargeable cell creation has been started in the beginning of 70s of last century from the development of the primary cells having lithium anode.
In lithium-ion rechargeable cell the positive electrode LixMeOy (M-Co or Ni, or Mn) is the source of lithium ions, but negative carbon-graphite plate is the receiver of these ions. Thereat, during cycling at the anode intercalation of lithium ions into the crystalline lattice under charging and their de-intercalation under discharging take place.
Lithium salt dissolved in the aprotic organic compounds is used as an electrolyte.
The summary process of lithium-ion cell operation can be presented by the equation:
Li MO2 + 6 C Li (1-x) MO2 +Lix C6
Lithium-ion cells are produced of prismatic, button and cylindrical types. The negative electrodes of lithium-ion cells are manufactured, as a rule, by pasting of active mass consisting of graphite and binder which is dissolved in organic solvent, onto the copper foil. The positive plates are also produced by pasting of active mass which includes active cathode reagent, electroconductive additive and binder, onto Al foil. Separator is made of polypropylene and polyethylene.
The absence of high-active, from chemical point of view, lithium in lithium-ion rechargeable cells makes them almost safe systems. The replacement of process of deposition and solution of metallic lithium by process of lithium ions migration from one electrode to other allows to increase the service life almost unlimitedly (up to several thousands and more cycles).
- High specific characteristics
- Stability to mechanical loads
- Long service life
- Low self-discharge
Comparative Characteristics of Sealed Rechargeable Cells
|Nominal voltage, V||3,6||1,25||1,2||1,25|
|Specific mass energy, Wh/kg||130||60—75||40—45||50—55|
|Specific volume energy, Wh/dm3||260||180—200||80—100||100—120|
|Self-discharge, % (day)||Äî 15 (28)||20 (28)||20 (28)||40(3)|
|Max excessive pressure, MPa||0,15||0,15||12|
|Capacity efficiency, %||98||96-98||72||90—92|
|Service life, years/cycles||5/500||5/500||5/500||7/1000|
Lithium-Ion Rechargeable Cells and batteries on Their Base
At present in a number of countries lithium-ion rechargeable cells are produced in a large scale and used worldwide as a power source for portable electronic devices (mobile phones, portable computers, video camcorders and so on).
At the same time the intensive research in the field of active electrode materials, electrolytes, separators and other components improvement are being carried out. To increase the consumer parameters of lithium-ion rechargeable cells (stabilization of electrical characteristics, increase of service life, expansion of working temperature range, increase of specific energy, improvement of production technology and decrease of cost — See the table on the previous page).
But already today the scientific and experimental reserve which is enough to make the power sources capable to replace the traditional power sources for such consumers as electric transport means, underwater and space apparatus has been created. Thereat, lithium-ion rechargeable cells are capable to provide the objects with power by 1,5 – 2,5 times more in comparison with traditional chemical power sources. The comparative characteristics of the rechargeable cells of different electrochemical systems are given in Table at previous page.
At present “NIAI “Istochnik” has the existing developments for lithium-ion rechargeable cells of cylindrical type within R6 size and for a number of prismatic rechargeable cells of 0,4 - 40 Àh capacity as well as for batteries on their base.
|Nominal capacity, Àh||18||25||0,4|
|Nominal discharge voltage, 0,1Ñ, V||3,6||3,6||3,6|
|Cycling life, cycles||300||300||500|
|Working temperature, °Ñ||-ÇÎäî+3||- 30 äî +50||- 20 äî +60|