# US 12,218,316 B2 · Convection-enhanced electrochemical energy storage devices and related methods

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- Number: US 12,218,316 B2
- Document ID: US12218316B2
- Status: Granted
- Kind: B2
- Application number: 17/504,909
- Filed: 2021-10-19
- Published: 2022-04-21
- Granted: 2025-02-04
- Earliest claimed: 2020-10-19
- Assignees: Massachusetts Institute of Technology
- Applicants: Massachusetts Institute of Technology
- Inventors: Fikile Richard Brushett; Weiran Gao; Javit Drake; Michael Orella
- Web page: https://patentgrep.com/patent/US12218316B2

## CPC

- H01M 10/4214: {Arrangements for moving electrodes or electrolyte}
- H01M 10/0563: Liquid materials, e.g. for Li-SOCl2 cells
- H01M 4/133: Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M 4/134: Electrodes based on metals, Si or alloys
- H01M 4/505: of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
- H01M 4/525: of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
- H01M 4/587: for inserting or intercalating light metals
- H01M 2004/027: {Negative electrodes}
- H01M 2004/028: {Positive electrodes}
- H01M 2300/0028: characterised by the solvent
- Y02E 60/10: Energy storage using batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A convection enhanced energy storage system includes an electrochemical cell with a positive electrode, a separator, and a negative electrode, a tank holding an electrolyte, and a pump connected to the electrochemical cell and the tank to circulate the electrolyte. The electrochemical cell has large γ and β values, which has high transport resistance from diffusion and there is limited salt in the electrolyte solution to compensate. A computer system can implement a model of a convection enhanced energy storage system, for example for simulation to select parameters for such an energy storage system. The model includes: a convection term in a Nernst-Planck equation representing the convection enhanced energy storage system; boundary conditions of a cell of the convection enhanced energy storage system to account for forced convection at boundaries; gauging conservation of anions within an external tank; and calculating electrode active area as a function of porosity.

## Claims

### Claim 1

A method for determining upper and/or lower limits of convection in a flow cell battery, the method comprising:
circulating a single electrolyte comprising an electroactive species in an electrochemical cell comprising a positive electrode, a separator, a negative electrode, wherein the electromigrative flux of the electroactive species is greater than the sum of the diffusive flux of the electroactive species and the convective flux of the electrolyte;
applying a voltage between the positive electrode and the negative electrode to generate an electromigrative flux of the electroactive species; and
circulating the single electrolyte in the electrochemical cell, wherein the electromigrative flux of the electroactive species is less than a sum of the diffusive flux of the electroactive species and the convective flux of the electrolyte.

### Claim 2

A method for determining upper and/or lower limits of convection in a flow cell battery, the method comprising:
circulating a single electrolyte in an electrochemical cell comprising a positive electrode, a separator, a negative electrode, wherein the electromigrative flux of the electroactive species is greater than the sum of the diffusive flux of the electroactive species and the convective flux of the electrolyte; and
applying a voltage between the positive electrode and the negative electrode to generate an electromigrative flux of an electroactive species; and
circulating the single electrolyte in the electrochemical cell, wherein a ratio of an applied current density to an effective diffusivity is greater than 1 and wherein a ratio of a convective flowrate to an initial electrolyte concentration is greater than 1.

### Claim 3 (depends on 2)

The method of claim 2, wherein:
I
app
⁡
(
1
-
t
+
)
⁢
L
F
⁢
⁢
D
eff
⁢
c
initial
>
0.5
⁢
⁢
and
⁢
⁢
Q
A
⁡
(
1
-
t
+
)
F
⁢
⁢
c
initial
⁢
ɛ
⁢
⁢
L
>
0.5
,
where Iapp defines an applied current density, t+ defines a transference number of the electroactive species of the electrolyte, L defines a dimension of the electrochemical cell or electrode, Deff defines an effective diffusivity of the electrolyte, cinitial defines the initial concentration of the electrolyte, QA defines an areal capacity of the electrochemical cell or electrode, and ε defines an electrode porosity.

### Claim 4 (depends on 2)

The method of claim 2, wherein:
the electrochemical cell satisfies
I
app
⁡
(
1
-
t
+
)
⁢
L
F
⁢
⁢
D
eff
⁢
c
initial
+
F
⁢
⁢
v
⁢
⁢
c
initial
⁢
L
<
3
,
where Iapp defines an applied current density, t+ defines a transference number of the electroactive species of the electrolyte, L defines a dimension of the electrochemical cell or electrode, Deff defines an effective diffusivity of the electrolyte, cinitial defines the initial concentration of the electrolyte, and v defines the flow velocity.

### Claim 5 (depends on 1)

The method of claim 1, wherein circulating comprises flowing the single electrolyte with an average velocity of greater than or equal to 0.001 μm/s and/or less than or equal to 10,000 μm/s.

### Claim 6 (depends on 1)

The method of claim 1, wherein a thickness of the positive electrode is greater than or equal to 5 μm and/or less than or equal to 5 cm.

### Claim 7 (depends on 1)

The method of claim 1, wherein a thickness of the negative electrode is less than or equal to 5 μm and/or less than or equal to 5 cm.

### Claim 8 (depends on 1)

The method of claim 1, wherein the single electrolyte has an effective diffusivity of greater than or equal to 1×10−10 cm2/s and/or less than or equal to 1×10−1 cm2/s.

### Claim 9 (depends on 1)

The method of claim 1, wherein the electrolyte has an initial electrolyte concentration of greater than or equal to 10 mM and/or less than or equal to 5 M.

### Claim 10 (depends on 1)

The method of claim 1, wherein a porosity of the positive electrode and/or the negative electrode is greater than or equal to 20% and less than or equal to 70%.

### Claim 11 (depends on 1)

The method of claim 1, wherein the electromigrative flux of the electroactive species is less than three times a sum of the diffusive flux of the electroactive species and the convective flux of the electrolyte.

### Claim 12 (depends on 1)

The method of claim 1, further comprising charging and/or discharging at a C-rate of greater than or equal to 0.001 h−1 and less than or equal 1,000 h−1.

### Claim 13 (depends on 1)

The method of claim 1, wherein the electrochemical cell is part of a system comprising:
the positive electrode comprising a lithium intercalation compound;
the separator adjacent to the positive electrode;
the negative electrode adjacent to the separator, the negative electrode comprising lithium-intercalated graphite or lithium metal;
a tank holding a single electrolyte;
a pump connected to the tank to circulate the single electrolyte; and
a processor operatively associated with the system, wherein the processor is configured to circulate and circulate the single electrolyte,
wherein the pump is configured to provide an average flow rate to the electrolyte of greater than or equal to 0.001 μm/s.

### Claim 14 (depends on 13)

The method of claim 13, wherein the pump is configured to provide an average flow rate to the electrolyte of greater than or equal to 0.5 μm/s or greater than or equal to 2.1 μm/s.

### Claim 15 (depends on 13)

The method of claim 13, wherein the positive electrode comprises a nickel-manganese-cobalt oxide compound.

### Claim 16 (depends on 13)

The method of claim 13, wherein the negative electrode comprises graphite.

### Claim 17 (depends on 13)

The method of claim 13, wherein the separator comprises polyvinylidene difluoride.

### Claim 18 (depends on 13)

The method of claim 13, further comprising a current collector adjacent to the positive electrode and/or the negative electrode.

### Claim 19 (depends on 13)

The method of claim 13, wherein the single electrolyte comprises lithium hexafluorophosphate.

### Claim 20 (depends on 13)

The method of claim 13, wherein the single electrolyte comprises ethylene carbonate, ethyl methyl carbonate, and/or vinylene carbonate.

### Claim 21 (depends on 1)

The method of claim 1, further comprising a processor operatively associated with the electrochemical cell, wherein the processor is configured to circulate and/or recirculate the single electrolyte.