Alkaline elctrochemical cells
AssigneeEveready Battery Company, Inc.
InventorChristhoper Fred Randell
Life of this patent
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Abstract
Alkaline electrochemical cells containing no added mercury and having a concentration of potassium hydroxide in the electrolyte, prior to discharge, of between about 34 and 37% (w/v solution) and wherein the amount of electrolyte is such that, after a calculated level of one electron discharge of the manganese dioxide, the calculated concentration of potassium hydroxide is between 49.5 and 51.5% (w/v solution), have superior performance in intermittent discharge tests.
Claims23
An alkaline electrochemical cell containing no added mercury and comprising:
- an aqueous potassium hydroxide electrolyte;
- a zinc-containing anode;
- and
- a manganese dioxide-containing cathode;
- characterised in that, prior to discharge, the concentration of potassium hydroxide in the electrolyte is between about 34 and 37% (w/v solution) and the amount of electrolyte is such that, at a calculated level of one electron discharge of the manganese dioxide, the calculated concentration of potassium hydroxide is between 49.5 and 51.5% (w/v solution).
A cell according to any preceding claim, wherein, prior to discharge, the concentration of potassium hydroxide in the electrolyte is about 36%, or slighter lower.
A cell according to any preceding claim having zinc oxide added only to the anode.
A cell according to any preceding claim, having an A:C ratio of about 1.33:1.
A cell according to any preceding claim, wherein the ratio of cathode capacity:
- cell volume is in the range of 0.47 to 0.50 Ah/cm3, where cathode capacity is calculated in accordance with the 1 electron principle.
A cell according to any preceding claim having a porosity of at least 67%, and comprising non-granular zinc.
A cell according to any preceding claim, having an anode porosity of between 66 and 76%, and comprising non-granular zinc in an amount of about 5% w/w.
A cell according to any preceding claim, which has a porosity of 70% to 76%.
A cell according to any preceding claim, wherein the anode contains from 60 to 77% (w/w) zinc.
A cell according to any preceding claim comprising a separator which comprises a copolymer of:
- (1) an ethylenically unsaturated carboxylic acid of formula (I):
- 3
- (where:
- R1, R2 and R3 are the same as or different from each other and each represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms or an aryl group;
- and A represents a direct bond or an alkylene group having up to 8 carbon atoms) or a salt or ester thereof;
- and
- (2) an aromatic compound of formula (II):
- 4
- (where:
- R4, R5 and R6 are the same as or different from each other and each represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms or an aryl group;
- and R7 represents a sulphonate or carboxylate group and balancing cation) or the separator comprises a homopolymer of said aromatic compound of formula (II). In general, it is preferred that A is a direct bond and R1-R7 are all hydrogen.
A cell according to any preceding claim for use in intermittent-use devices.
A cell according to any preceding claim which, when discharged at a constant resistance of 3.9 Ω for 1 hours per day with a rest period of 23 hours per day, reaches an endpoint voltage of 0.8 V only after a total of at least 480 minutes discharge time.
Dependencies are inferred from the claim text.