# US 2019/0245250 A1 · Lithium-ion battery formation process

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- Number: US 2019/0245250 A1
- Document ID: US20190245250A1
- Status: Published application
- Kind: A1
- Application number: 16/077,797
- Filed: 2016-03-25
- Published: 2019-08-08
- Earliest claimed: 2016-03-25
- Assignees: Toyota Motor Europe; Toyota Jidosha Kabushiki Kaisha
- Applicants: Toyota Motor Europe; Toyota Jidosha Kabushiki Kaisha
- Inventors: Takahiro SAKURAI; Tomohide SUMI; Yoshio MATSUYAMA
- Web page: https://patentgrep.com/patent/US20190245250A1

## CPC

- H01M 10/4235: {Safety or regulating additives or arrangements in electrodes, separators or electrolyte (H01M10/4242 takes precedence)}
- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- H01M 10/0567: characterised by the additives
- H01M 10/446: {Initial charging measures}
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- 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
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method of performing a formation process for a lithium-ion cell having an anode, a cathode, an electrolyte and a separator, the formation process including adding an additive to the electrolyte for improving a solid electrolyte interface build-up on the anode, performing a first charge of the cell at a first predetermined rate, performing a cycle of discharging/charging the cell at the first predetermined rate, repeating the cycle until a cycle maximum dQ/dV peak value is smaller than or equal to a predetermined dQ/dV value during charging of the cell and charging the cell to a fully charged capacity at a second predetermine rate, the second predetermined rate being greater than the first predetermined rate.

## Claims

### Claim 1

A method of performing a formation process for a lithium-ion cell having an anode, a cathode, an electrolyte and a separator, the formation process comprising:
adding an additive to the electrolyte for improving a solid electrolyte interface build-up on the anode;
performing a first charge of the cell at a first predetermined rate, the first charge comprising:
calculating dQ/dV during the first charge;
detecting a peak in the dQ/dV curve;
determining an end of peak voltage value and a maximum peak voltage value corresponding to a first maximum dQ/dV peak value, the end of peak voltage value being a voltage at which a dQ/dV value is smaller than or equal to a first predetermined dQ/dV value;
stopping the first charge at the end of peak voltage value;
performing a cycle of discharging/charging the cell at the first predetermined rate, the cycle comprising:
discharging the cell between the end of peak voltage value and a threshold voltage value;
charging the cell between the threshold voltage value and the end of peak voltage value;
repeating the cycle until a cycle maximum dQ/dV peak value is smaller than or equal to a second predetermined dQ/dV value during charging of the cell; and
charging the cell to a fully charged capacity at a second predetermine rate, the second predetermined rate being greater than the first predetermined rate.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the first predetermined dQ/dV value is smaller than or equal to 20% of the first maximum dQ/dV peak value.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the cycle is repeated until the peak is no longer present.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the first predetermined rate is smaller than or equal to 2 C.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the second predetermined rate is equal to or greater than 2 C.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the threshold voltage value is calculated according to the following equation:
Vthresh=Vend−2*(Vend−Vpeak)

### Claim 7 (depends on 1)

The method according to claim 1, wherein the additive presents at least a dQ/dV peak below a main flat voltage value of the anode.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the additive provided in the electrolyte is selected from an oxalate salt, an ethylene carbonate or a sulfone.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the first predetermined rate is chosen as a function of the additive.

### Claim 10 (depends on 1)

The method according to claim 1, comprising:
defining a group of cells, each cell of the group of cells having an anode, a cathode, an electrolyte and a separator respectively of the same type as the anode, the cathode, the electrolyte and the separator of the cell;
then for each cell of the group of cells:
adding the additive to the electrolyte;
performing the first charge at the first predetermined rate up to the end of peak voltage value;
performing the cycle of discharging/charging at the first predetermined rate between the threshold voltage value and the end of peak voltage value a number of times determined in claim 1;
charging to the fully charged capacity at the second predetermine rate.

### Claim 11 (depends on 1)

The method according to claim 1, wherein the first predetermined dQ/dV value is smaller than or equal to 10% of the first maximum dQ/dV peak value.

### Claim 12 (depends on 1)

The method according to claim 1, wherein the first predetermined rate is smaller than or equal to 1 C.

### Claim 13 (depends on 1)

The method according to claim 1, wherein the first predetermined rate is smaller than or equal to 0.5 C.

### Claim 14 (depends on 1)

The method according to claim 1, wherein the second predetermined rate is equal to or greater than 3 C.

### Claim 15 (depends on 1)

The method according to claim 1, wherein the second predetermined rate is equal to or greater than 4 C.