Substituted lambda manganese dioxides in an alkaline electrochemical cell
Substituted λ-MnO 2 compounds are provided, where a portion of the Mn is replaced by at least one alternative element. Electrochemical cells incorporating substituted λ-MnO 2 into the cathode, as well as methods of preparing the substituted λ-MnO 2 , are also provided.
1. Substituted λ-MnO 2 , having at least one alternate element substituted for a portion of the Mn;
wherein the substituted k-MnO 2 has the formula (Li 1-v A v ) z (Mn 1-x M x )O 2-(w/2) AS (t/2) , wherein 0<x≤0.5, v≤0.1, 0<z≤0.10, and t≤w≤0.2, wherein M is the at least one alternate element, wherein A is an alkali metal, and wherein AS is S, F, N, or any element that can be isoelectronic to O 2− ; or
wherein the substituted λ-MnO 2 has the formula (Li 1-v A v ) z (Mn 1-x-y M1 x M2 y )O 2-(w/2) AS (t/2) , wherein 0<(x+y)≤0.5, v≤0.1, 0<z≤0.10, and t≤w≤0.2, wherein M1 and M2 are each an alternate element, wherein M1 is different from M2, wherein A is an alkali metal, and wherein AS is S, F, N, or any element that can be isoelectronic to O 2− .
2. The substituted λ-MnO 2 of claim 1 , wherein z<0.05.
3. The substituted λ-MnO 2 of claim 1 , wherein the at least one alternate element is selected from the group consisting of Al, B, Co, Cr, Cu, Fe, Ga, Li, Nb, Ni, Mg, Ru, Ti, V, and Zn, and A is selected from the group consisting of Na, K, Rb, and Cs.
4. The substituted λ-MnO 2 of claim 1 , wherein the at least one alternate element can exist in an octahedral coordination environment of oxygen, supports M-O bonds of about 1.8 to 2.2 Å, and has an oxidation state that allows charge neutrality of the λ-MnO 2 .
5. A primary alkaline electrochemical cell comprising a cathode comprising the substituted λ-MnO 2 of claim 1 , wherein the substituted λ-MnO 2 comprises two alternate elements, and wherein the electrochemical cell exhibits a synergistic improvement in specific capacity or runtime compared to an electrochemical cell comprising a cathode comprising unsubstituted λ-MnO 2 .
6. A primary alkaline electrochemical cell, comprising:
a) a container; and
b) an electrode assembly disposed within the container and comprising a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an alkaline electrolyte,
wherein the negative electrode comprises zinc, and
wherein the positive electrode comprises the substituted λ-MnO 2 of claim 1 .
7. The primary alkaline electrochemical cell of claim 6 , wherein the specific capacity or runtime is greater than that of a similar primary alkaline electrochemical cell comprising unsubstituted λ-MnO 2 or EMD in its positive electrode.
8. The primary alkaline electrochemical cell of claim 6 , wherein the specific capacity is between 267-359 (mAh/g to 0.9V), or between 285-350 (mAh/g to 0.9V), or between 295-340 (mAh/g to 0.9V), or between 305-335 (mAh/g to 0.9V), or between 315-330 (mAh/g to 0.9V), or between 320-325 (mAh/g to 0.9V).
9. The primary alkaline electrochemical cell of claim 6 , wherein during discharge, formation of Birnessite is delayed, reduced, or eliminated compared to the formation of Birnessite during discharge of a similar primary alkaline electrochemical cell comprising unsubstituted λ-MnO 2 or EMD in its positive electrode.
10. The substituted λ-MnO 2 of claim 1 , wherein the substituted λ-MnO 2 comprises the alkali metal.
11. The substituted λ-MnO 2 of claim 1 , wherein the substituted λ-MnO 2 comprises oxygen vacancies.
12. The substituted λ-MnO 2 of claim 1 , wherein the substituted λ-MnO 2 comprises at least one anion substituent.
13. A method of producing a substituted λ-MnO 2 , comprising the step of suspending a composition having the chemical formula (Li 1-v A v )Mn 2-2x M 2x )O 4-w AS t in aqueous sulfuric acid,
so as to produce a substituted λ-MnO 2 having the formula (Li 1-v A v ) z (Mn 1-x M x )O 2-(w/2) AS (t/2) ,
wherein 0<x≤0.5, v≤0.1, 0≤z≤0.05, and t≤w≤0.2; and
wherein M is selected from the group consisting of Al, B, Co, Cr, Cu, Fe, Ga, Li, Nb, Ni, Mg, Ru, Ti, V, and Zn, A is selected from the group consisting of Na, K, Rb, and Cs, and AS is selected from the group consisting of S, F, and N.
14. The method of claim 13 , further comprising a step of producing the (Li 1-v A v )(Mn 2-x M 2x )O 4-w AS t by reacting Li 2 CO 3 , A 2 CO 3 if A is present, Mn 2 O 3 , O 2 , a compound comprising M, and a compound comprising AS if AS is present, in appropriate stoichiometric ratios, at about 850° C.
15. A substituted λ-MnO 2 produced by the method of claim 13 .
16. A primary alkaline electrochemical cell, comprising:
a) a container; and
b) an electrode assembly disposed within the container and comprising a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an alkaline electrolyte,
wherein the positive electrode comprises substituted λ-MnO 2 produced by the method of claim 13 .
17. A method of producing a substituted λ-MnO 2 , comprising the step of suspending a composition having the chemical formula (Li 1-v A v )(Mn 2-2x-2y M1 2x M2 2y )O 4-w AS t in aqueous sulfuric acid,
so as to produce a substituted λ-MnO 2 having the formula
(L 1-v A v ) z (M1 1-x-y M1 x M2 y )O 2-(w/2) AS (t/2) ,
wherein 0<(x+y)≤0.5, v≤0.1, 0≤z≤0.05, and t≤w≤0.2; and
wherein M1 and M2 are different from each other and are each selected from the group consisting of Al, B, Co, Cr, Cu, Fe, Ga, Li, Nb, Ni, Mg, Ru, Ti, V, and Zn, A is selected from the group consisting of Na, K, Rb, and Cs, and AS is S, F, N, or any element that can be isoelectronic to O 2− .