Varta Batterie Aktiengesellschaft

Rudolf Herr

Rainer Bittihn

Hans-Walter Praas

Detlev Hoge

Detley Hoge

The invention relates to a lithium ion cell, comprising a positive electrode which contains a chalkogen compound, containing lithium, of a transition metal, a non-aqueous electrolyte and a negative electrode which is separator-isolated and contains carbon, which is characterized in that the cell contains lithium metal or a lithium alloy in a form physically separated from the electrodes, the lithium metal or the lithium alloy having a connection for the main lead of an electrode and, via the electrolyte, an ionic connection for the electrodes.

Lithium ion cell

Nontoxic, chemically stable lithium tris(fluorosulphonyl)methanide, LiC(SO.sub.2 F).sub.3, is used as a conducting salt for rechargeable lithium cells containing nonaqueous electrolytes based on esters or polymeric electrolytes such as polyethylene oxide. The cell electrolyte is preferably comprised of an approximately 1 molar solution of the salt in a mixture of 50% by volume of ethylene carbonate (EC) and 50% by volume of diethyl carbonate (DEC).

Rechargeable galvanic lithium cell

An electrochemical secondary element with a non-aqueous electrolyte, whose charge/discharge mechanism is predicated upon the reversible intercalation of active Li+ ions in electrode materials having an open skeletal structure. The positive electrode is essentially a lithium-manganese spinel of the type Li.sub.q M.sub.x Mn.sub.y O.sub.z which, in addition to satisfying the expressions 0&lt;x&lt;0.6 and 1.4&lt;y&lt;2.0, can also contain up to 30% of other metals such as Co, in addition to Mn. The negative electrode is based on a carbon product obtained by pyrolysis from organic compounds, and serves as the recipient substance for the Li+ ions. By limiting the Li concentration in the spinel lattice to a range in which the numerical values of the variable q lie between 0 and 1.3, a lithium-poor manganese spinel is obtained. During discharging of the preponderant portion of the secondary element's capacity, the result is that a cell potential greater than 3 volt is obtained, and high cycling stability is also manifested.

Electrochemical secondary element

In a lithium secondary cell of the intercalation type, with a positive electrode which includes a lithiated transition metal oxide Li.sub.x M.sub.y O.sub.2, wherein 0.5.ltoreq.x/y.ltoreq.1.0 and M is a metal from Groups VIIb and VIIIb (preferably Co, Ni, Mn), and with a negative electrode formed of a carbon product with disordered crystalline structure produced from organic materials by delayed coking, both electrodes are uncharged in the initial assembly state, but the negative electrode is doped with lithium through prelithiation in an amount which is irreversibly consumed in the formation of ion conductive surface layers. This permits a loss-free deintercalation of any subsequently introduced lithium so that the cell exhibits, from its inception, a largely stable capacity during cyclic charge/discharge operation.

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Kelkheim, Germany

Rudolf Herr