Electrodes, electrochemical cells, and methods for making electrodes
Electrodes, electrochemical cells and methods for making electrodes are provided. In one example, an electrode includes an electrode base material. The electrode further includes an oxygen-scavenger material that is disposed on the electrode base material.
1 . An electrode for an electrochemical cell, the electrode comprising:
an electrode base material that is a positive electroactive material configured as particles having respective outer surfaces; and
an oxygen-scavenger material that is an intermediate oxidation state compound coated overlying the respective outer surfaces of the particles;
wherein the intermediate oxidation state compound is capable of chemically reacting with oxygen released from the electrode base material during at least one of use, cycling, and charging of the electrochemical cell at a state of charge of about 80% or greater to be consumed and form a product compound having a higher degree of oxidation than the intermediate oxidation state compound, such that the oxygen is chemically bound in the product compound and is no longer available as a reactive gas within the electrochemical cell.
2 . The electrode of claim 1 , wherein the intermediate oxidation state compound is one of an intermediate oxidation state inorganic compound and an intermediate oxidation state organic compound.
3 . The electrode of claim 1 , wherein the oxygen-scavenger material is chosen from FeCO 3 , NaSO 3 , Na 2 SO 3 , poly 3-(methylsulfinyl)prop-1-ene, poly acrylic (bis(2,2,2,-trifluoroethyl)phosphorous) anhydride, or combinations thereof.
4 . The electrode of claim 1 , wherein the oxygen-scavenger material is present in an amount of from about 1 wt. % to about 20 wt. %, based on a total weight of the electrode.
5 . The electrode of claim 1 , wherein the electrode is a cathode and the positive electroactive material comprises Mn, Ni, Co, Cr, Fe, V, Li, or a combination thereof.
6 . The electrode of claim 1 , further comprising a binder that holds the particles coated with the oxygen-scavenger material together.
7 . The electrode of claim 6 , further comprising conductive particles that are dispersed throughout the electrode together with the particles coated with the oxygen-scavenger material.
8 . An electrochemical cell comprising:
a positive electrode comprising:
a positive electrode base material configured as particles having respective outer surfaces; and
an oxygen-scavenger material that is an intermediate oxidation state compound coated overlying the respective outer surfaces of the particles;
wherein the intermediate oxidation state compound is capable of chemically reacting with oxygen released from the positive electrode base material during at least one of use, cycling, and charging of the electrochemical cell at a state of charge of about 80% or greater to be consumed and form a product compound having a higher degree of oxidation than the intermediate oxidation state compound, such that the oxygen is chemically bound in the product compound and is no longer available as a reactive gas within the electrochemical cell;
a negative electrode;
a separator disposed between the positive and negative electrodes, wherein the separator is electrically insulating and ionically conductive; and
an electrolyte operatively disposed between the positive and negative electrodes and interfacing with the separator to conduct ions between the positive and negative electrodes.
9 . D) A method for making an electrode of an electrochemical cell, the method comprising:
coating respective outer surfaces of particles of a positive electrode base material with an oxygen-scavenger material that is an intermediate oxidation state compound such that the intermediate oxidation state overlies the respective outer surfaces of the particles to form a coated electrode base powder;
wherein the intermediate oxidation state compound is capable of chemically reacting with oxygen released from the positive electrode base material during at least one of use, cycling, and charging of the electrochemical cell at a state of charge of about 80% or greater to be consumed and form a product compound having a higher degree of oxidation than the intermediate oxidation state compound, such that the oxygen is chemically bound in the product compound and is no longer available as a reactive gas within the electrochemical cell; and
binding the coated electrode base powder together with a binder.
10 . The method of claim 9 , wherein coating the particles comprises:
forming a slurry that comprises the particles of the positive electrode base material; and
reacting one or more oxygen-scavenger precursor materials in the slurry at reaction conditions to form the coated electrode base powder.
11 . The method of claim 10 , wherein the oxygen-scavenger material comprises FeCO 3 , wherein forming the slurry comprises forming the slurry that furthers comprises cathode active materials, Fe(NO 3 ) 3 ·9H 2 O, urea, and tetraethoxysilane (TEOS), and wherein reacting the one or more oxygen-scavenger precursor materials comprises heating and pressurizing the slurry at the reaction conditions that include a temperature of from about 180° C. to about 220° C., a pressure of from about 1.5 atm to about 10 atm, and for a time of from about 1 hour to about 72 hours.
12 . The method of claim 10 , wherein the oxygen-scavenger material comprises NaSO 3 , wherein forming the slurry comprises forming the slurry that furthers comprises NaOH and/or Na 2 CO 3 , cathode active materials and water, and wherein reacting the one or more oxygen-scavenger precursor materials comprises exposing the slurry to SO 2 at the reaction conditions that include a temperature of from about 10° C. to about 60° C., and for a time of from about 30 minutes to about 24 hours.
13 . The method of claim 10 , further comprising:
removing the coated electrode base powder from the slurry;
rinsing the coated electrode base powder with a solvent; and
drying the coated electrode base powder.
14 . The method of claim 13 , wherein removing the coated electrode base powder comprises filtering out the coated electrode base powder from the slurry, and wherein drying the coated electrode base powder comprises drying the coated electrode base powder at a temperature of from about 70° C. to about 130° C. for a time of from about 1 hours to about 24 hours.
15 . The method of claim 9 , wherein binding the coated electrode base powder comprises:
forming a mixture comprising the coated electrode base powder, the binder, and optionally a solvent; and
forming the electrode using the mixture, wherein the electrode comprises the coated electrode base powder held together by the binder.
16 . The method of claim 15 , wherein forming the mixture comprises forming the mixture further comprising conductive particles, and wherein forming the electrode comprises forming the electrode comprising the conductive particles and the coated electrode base powder held together by the binder.