Comparison of Solid State Lithium Batteries Assembled with Li1.5Al0.5Ge1.5P3O12(LAGP) and Li2Al2SiP2TiO13 (LICGC) Solid Electrolyte Sheets
This application note shows the assembling and testing operations of solid state lithium batteries with
Li1.5Al0.5Ge1.5P3O12 (LAGP) and Li2Al2SiP2TiO13 (Lithium Ion Conductive Glass Ceramic, LICGC) solid electrolyte
sheets. The performance of LAGP and LICGC solid state lithium batteries are compared.

Experimental Materials and Equipments
Solid Electrolyte Sheets
LAGP

LICGC

Li1.5Al0.5Ge1.5P3O12 Conductive Ceramic Separator
Sheets with Optional Sizes for Li-Air & Solid
Rechargeable Batteries - EQ-LAGP-LD

Li2Al2SiP2TiO13 Conductive Glass Ceramic Separator
Sheets with Optional Sizes for Li-Air Batteries - EQCGCS-LD

Sale Price: USD$249.00

Sale Price: USD$298.00

Cathode, Anode, Separator, and Liquid Electrolyte
CathodeAnode

Li-Ion Battery Cathode - Aluminum Foil Single Side
Coated by LiCoO2 (241 mm L x 200 mm W x 55 um
Thickness) 5 sheets/bag - bc-af-241co-ss-55

Lithium Chip 15.6 mm Dia x 0.25 mm thickness for Liion Battery R&D 100 g/bottle (4000 pcs) - EQ-Lib-LiC25

Sale Price: USD$189.95

Sale Price: USD$459.00

Separator

Liquid Electrolyte

Ceramic Coated Membrane (16 um thick x 60 mm W x
500 mL) as Separator of Li-ion Battery - EQ-bsf-0016500A

Electrolyte LiPF6 for LiCoO2 Lithium-ion Battery R&D,
1 kg in Stainless Steel Container - EQ-LBC3051C

Sale Price: USD$498.00

Sale Price: USD$549.00

Equipments
Split Cell

PipettePressure Controlled Split Coin Cell with Optional Size up
to 20 MPa For SSB Research - EQ-PSC

Precision Electronic Single Channel Pipette: 20 – 200 uL
with Battery & Charger - BD-200UL-LD

Sale Price: USD$589.00

Sale Price: USD$495.00

Disc Cutter

Glove Box

Compact Precision Disc Cutter with 4 Sets of Cutting Die(15, 19, 20 & 24 mm) - MSK-T-07

Glove Box with H2O & O2 Purification System andOpenable Front Window - EQ-VGB-6OP-LD

Sale Price: USD$1,998.00

Sale Price: RFQ

Press

Load Cell

1T Compact Pneumatic Compressing Jig - YLJ-01

Pressure Calibration Kit: NIST certificated Load cell +Digital Meter - BS-070-LD

Sale Price: USD$1,995.00

Sale Price: USD$1,469.00

Battery Analyzer

8 Channel Battery Analyzer (0.005 -1 mA, up to 5 V) w/
Adjustable Cell Holders Laptop & Software - BST8-WA
Sale Price: USD$3,698.00

Solid State Lithium Battery Assembly
Experimental Setup and Battery AssemblyLaboratory Press
Load Cell
Stainless Steel Top Pressing Rod - AnodeNylon Gasket Compression Nut
Sealing O-ring
Nylon Split Cell, 20 mm ID
Solid-State Lithium Battery
Stainless Steel Bottom Pressing Rod - Cathode
PTFE Insulator

Fig. 1 Schematic of the split cell experimental setup.

Li Metal Chip Anode, 15.6 mm Dia.
LiPF6 Liquid Electrolyte, 20 µL
Al2O3 Coated PE Separator, 19 mm Dia.
Solid Electrolyte, LAGP or LICGC, 19 mm Dia.
LiPF6 Liquid Electrolyte, 20 µL
LiCoO2 Coated Al Foil Cathode, 19 mm Dia.
Experiment 1

Experiment 2

No Liquid Electrolyte

Solid Electrolyte with Wetted Surface

Fig. 2 Schematic of the solid state lithium battery assembled with solid state electrolyte.

Table 1 Specification of the assembled solid state lithium batteries.

Solid Electrolyte

LAGP or LICGC. 19 mm Dia. 0.3 mm or 0.15 mm Thickness
4 × 10-4 S/cm Ion Conductivity at 25 °C (See Table 2 for Details)

CathodeLiCoO2 Coated Al Foil, Single Sided
Cut into 19 mm Dia. Chip by Disc Cutter. 0.055 mm Thickness

Anode

Li Metal Chip
15.6 mm Dia., 0.25 mm Thickness

Separator

Al2O3 Coated Polyethylene (PE) Membrane.
Cut into 19 mm Dia. Chip by Disc Cutter. 0.016 mm Thickness

Liquid Electrolyte

1M LiPF6 Liquid Electrolyte. 1 × 10-2 S/cm Ion Conductivity at 25 °C
20 µL on Each Side of Solid Electrolyte. 40 µL Total

Pressing Rods

Stainless Steel Rods. 20 mm Dia.

Assembled Size

19 mm Dia., 0.62 mm (LAGP) or 0.47 mm (LICGC) Thickness

Specific Capacity LiCoO2

145 mAh/g (Reported)

LiCoO2 Weight

3.6 × 10-2 g (Reported)

Expected Capacity

5.2 mAh

Temperature

25 °C

Gas Environment

Glove box filled with high purity Ar gas. H2O and O2 level < 1 ppm

Table 2 Comparison between LAGP and LICGC solid electrolyte sheets.
LAGP

LICGC

Composition

Li1.5Al0.5Ge1.5P3O12

Li2Al2SiP2TiO13

Structure

NASICON (Na Super Ionic Conductor)

NASICON (Na Super Ionic Conductor)

Ion Conductivity at 25 °C

4 × 10-4 S/cm (Reported)

4 × 10-4 S/cm (Reported)

Average Grain Size

~25 µm (Reported)

1-10 µm (Reported)

Chemical Resistance

Water and Mild Acid Resistance

Water and Mild Acid ResistanceStable in Air and Water

Yes

Yes

Stable with Li Metal

Yes

No (Separator Needed)Size

19 mm Dia

19 mm Dia

Thickness

0.3 mm0.15 mmPart Number

EQ-LAGP-LD

EQ-CGCS-LDBattery Assembling Procedures
1.

Use the disc cutter to cut LiCoO2 (LCO) coated Al foil and Al2O3 coated polyethylene (PE) membrane into 19
mm Dia. chips. Move the experimental materials and equipments into the glove box from the openable front
window. Install the power, gas, and testing cable feedthroughs on the glove box. Seal the glove box, purge andcycle until both H2O and O2 levels drop < 1 ppm.

2.

Open the Li metal chip container only after both H2O and O2 levels drop < 1 ppm. Prepare the work space in the
glove box, and make sure the experimental materials and tools are ready for use.

3.

Use tweezers to put LCO/Al cathode chip on top of the bottom pressing rod with LCO coated side facing up.

4.

Use the digital pipette to draw 20 uL LiPF6 liquid electrolyte, and spread the liquid electrolyte evenly on thecathode chip. Put the solid electrolyte sheet (LAGP or LICGC) right on top of the wetted cathode chip. For
Experiment 1, no liquid electrolyte is used, and solid electrolyte sheet is directly put on top (See Fig. 2 fordetails).

5.

Due to the instability of LICGC solid electrolyte when in contact with Li metal, a separator between Li metal
anode and LICGC solid electrolyte sheet is needed for LICGC protection and dendrite growth prevention. Use
tweezers to put the Al2O3 coated PE separator chip on top of the solid electrolyte as a protection interlayer. Use
the digital pipette to draw 20 uL LiPF6 liquid electrolyte, and spread the liquid electrolyte evenly on the separator
chip. For Experiment 1, no liquid electrolyte is used. Also, no separator chip is used to ensure physical contact
between LICGC and Li metal anode when pressed together.

6.

Use tweezers to put the Li metal anode on top of the separator chip and solid electrolyte sheet. Make sure theanode chip is right at the center to avoid shorting between anode and cathode.

7.

Put the top pressing rod through the compression nut, and press the rod through the top sealing O-ring. Carefullypress down the top pressing rod until it is in contact with the Li metal anode. Rotate the gasket compression nut
tight to seal the assembled battery inside the split cell.

8.

Adjust the input gas pressure of the pneumatic press and set it to be the lowest pressure needed to raise thepressing stage. Insulate the top and bottom pressing rods of the split cell with the PTFE insulators. Position the
split cell at the center of the pneumatic press. Raise the pressing stage to hold the split cell in place. Gradually
adjust the input gas pressure and check the load cell force reading to reach the desired pressing force / pressure.

9.

Connect the split cell to the battery analyzer outside of the glove box using the testing cable feedthrough.
Connect the red clips to the bottom pressing rod (cathode); connect the black clips to the top pressing rod (anode).
Start the battery testing.

10. Please refer to the instruction video for details.

Fig. 3 Battery assembling procedures of solid state lithium battery.

Solid State Lithium Battery TestingExperiment 1 - Solid Electrolyte with No Liquid Electrolyte
Table 3 Experiment 1 – battery testing parameters.
Solid Electrolyte

LAGP

LICGC

Pressing Force

50 – 5000 N

Pressure

0.16 – 16 MPa

ChargeConstant Current Discharge to 5.0 V. Current – 0.5 mA, 0.1 mA, 0.05 mA

Discharge

Constant Current Discharge to 2.5 V. Current – 0.5 mA, 0.1 mA, 0.05 mA

Current Density

0.25 mA/cm2, 0.05 mA/cm2, 0.025 mA/cm2

For solid state lithium batteries assembled with no liquid electrolyte, the assembled battery shows very large internal
resistance.
A pressing force of 500 N (1.6 MPa pressure) is applied to the battery, and maintained during charge – discharge
cycles. For LAGP solid state battery, it shows an open circuit voltage of ~2.4 V before charging; while for LICGC
solid state battery, ~3.3 V before charging. When charged with a constant current as low as 0.05 mA, both batteries
quickly raise to 5.0 V, indicating very large internal resistance. After charging, the open circuit voltage cannot be
maintained, and will slowly drop to the initial voltage before charging (~2.4 V for LAGP, ~3.3 V for LICGC).
The cause of large internal resistance is attributed to the poor solid-solid interface contact between electrolyte sheet
and electrode chips. The resulting large interface resistance dominates the battery internal resistance, and making it
difficult to charge energy into the solid state batteries.
The pressing force is varied from 50 to 5000 N. No obvious change on the battery performance is observed. The
solid-solid interface contact between electrolyte sheet and electrode chips cannot be improved by increasing thepressing force (up to 5000 N) alone.

Experiment 2 - Solid Electrolyte with Liquid Electrolyte Wetted Surfaces
Table 4 Experiment 2 – battery testing parameters.
Solid Electrolyte

LAGP

LICGC

Pressing Force

500 N

500 N, 800 N

Pressure

1.6 MPa

1.6 MPa, 2.6 MPa

ChargeConstant Current Discharge to 4.3 V. Current – 0.5 mA

Discharge

Constant Current Discharge to 3.0 V. Current – 0.5 mA

Current Density

0.25 mA/cm2

For solid state lithium batteries with LiPF6 liquid electrolyte wetted solid electrolyte, the solid-solid interface contact
are greatly improved by the small amount of liquid electrolyte sandwiched between solid electrolyte sheet andelectrode chips. As a result, the battery performance is significantly improved compared to Experiment 1.
Figures of charge-discharge profile and cycle performance are shown in Fig. 4. A pressing force of 500 N (1.6 MPapressure) is applied to the battery, and maintained during charge – discharge cycles. For both LAGP and LICGC solidstate batteries, an open circuit voltage of ~3.1 V is observed before charging. Then, both batteries are tested withmultiple charge – discharge cycles, and the battery performance is compared between LAGP and LICGC solid
electrolytes. Moreover, the pressing force for the LICGC solid state battery is increased to 800 N (2.6 MPa pressure)
after 9 cycles to study the mechanical pressure effect.
Under the 500 N pressing force, LAGP solid state battery shows an initial specific capacity of 52 mAh/g at cycle 1,
and decreases linearly in the following cycles. At cycle 9, the specific capacity drops to 35 mAh/g. For LICGC solidstate battery tested under the same conditions, the specific capacity starts with a low value of 38 mAh/g at cycle 1,
and then increase rapidly to reach 93 mAh/g at cycle 3. After cycle 3, the specific capacity drops in a linear trend to
55 mAh/g at cycle 8. Both LAGP and LICGC solid state batteries give a high efficiency around 96% or higher
throughout the multiple cycles. In terms of battery capacity, the LICGC solid state battery with LiPF6 wetted solid
electrolyte exhibits better battery performance than the LAGP solid state battery.
To study the effect of pressing force on solid state lithium batteries with LiPF6 wetted solid electrolyte, the pressing
force is increased from 500 N (1.6 MPa) to 800 N (2.6 MPa) before the start of cycle 9 of LICGC solid state battery(See Fig. 4c). No significant improvement on battery performance is observed thereafter, while the specific capacity
keeps decreasing in the same linear trend over cycle / time. This result is expected, as the main improvement on thesolid-solid interface is from the incorporation of LiPF6 liquid electrolyte, which would not be affected much by ahigher mechanical pressure.

4.4
4.2

Voltage (V)

4.0
3.8

3.6
3.4
3.2
3.0
Cycle #

9

8 76 5 4

2 3 1

(a)

2.8
0

10

20

30
Capacity (mAh/g)

40

50

60

4.4
4.2

Voltage (V)

4.0
3.8

3.6
3.4
3.2
3.0

(b)
Cycle #

11

1 10

9

40

60
Capacity (mAh/g)

8

7

6

2

5

4

3

2.8
0

20

80

100

(c)

140.0

100

120.0
LICGC_Charge
LICGC_Discharge
LAGP_Charge
LAGP_Discharge
LICGC_Efficiency
LAGP_Efficiency

80.0

60

60.0

Efficiency (%)

Specific Capacity (mAh/g)

100.0

80

40
40.0
20
20.0

Increase Pressure from 1.6 to 2.6 MPa
at LICGC Cycle #9

0.0

0
0

2

4

6
Cycle Number

8

10

12

Fig. 4 (a) Charge-discharge profile of battery with LiPF6 surface wetted LAGP. (b) Charge-discharge profile ofbattery with LiPF6 surface wetted LICGC. (c) Comparison of cycle performance between LAGP and LICGC solidstate batteries. The batteries are charged / discharged at a constant current of 0.5 mA from 3.0 – 4.2 V.
After the above experiment of solid state lithium battery with LiPF6 surface wetted LAGP, the LAGP battery is
dissembled and 20 µL of LiPF6 liquid electrolyte is re-applied to each side of the LAGP solid electrolyte for rewetting the surfaces. Keeping the same LCO/Al cathode and Li metal anode from the previous experiment, the LAGP
solid state battery is re-assembled in the split cell with the re-wetted LAGP solid electrolyte. Then the battery is tested
under the same conditions as the previous experiment (500 N pressing force, same charge-discharge parameters). The
measured specific capacity goes back up and reaches the capacity of the original first cycle, which is ~52 mAh/g (SeeFig. 5). This reveals that the degradation of battery performance is mainly from the consumption / evaporation of thesmall amount of the LiPF6 liquid electrolyte sandwiched between LAGP and electrodes, which deteriorates the solid-solid interface contact, increases the interface resistance, and lowers the capacity over cycle / time.

90.0
100

80.0

LAGP_2

LAGP_1

80

60.0
50.0

60

40.0

LAGP_1_Charge
30.0

LAGP_1_Discharge
LAGP_2_Charge

20.0

Efficiency (%)

Specific Capacity (mAh/g)

70.0

40
Capacity goes back up after solid electrolyte
re-wetting / liquid electrolyte re-filling

LAGP_2_Discharge

20

LAGP_1_Efficiency

10.0

LAGP_2_Efficiency

0.0

0
0

2

4

6
8
Cycle Number

10

12

14

Fig. 5 Comparison of cycle performance between the original LAGP solid state battery (LAGP_1 in the figure) andthe re-assembled the LAGP solid state battery with LAGP solid electrolyte re-wetted (LAGP_2 in the figure). The
batteries are charged / discharged at a constant current of 0.5 mA from 3.0 – 4.2 V.

Conclusion
1.

The interface resistance between electrolyte sheets and electrode chips is crucial for the battery performance ofsolid state lithium batteries. Wetting the surfaces of solid electrolyte with a small amount of liquid electrolyte cangreatly reduce the interface resistance and improve the battery performance.

2.

The battery performance of LAGP and LICGC solid electrolytes are compared under the same testing conditions
and the LICGC battery exhibits higher battery capacity. The LICGC solid state battery with LiPF6 wetted solid
electrolyte achieves a specific capacity of 93 mAh/g at cycle 3, while the LAGP solid state battery with LiPF6
wetted solid electrolyte gives the highest specific capacity at cycle 1, which is 52 mAh/g.

3.

The pressing force has no obvious effect on the battery performance of solid state lithium battery assembled withsurface wetted solid electrolyte.