LiET’s Aluminum Graphite Dual ion Battery (AGDiB)

In a conventional lithium ion battery, the reversible inclusion or insertion of a molecule (or ion) into lithium ions in both cathode (i.e., LiCoO2, LiFePO4) and anode (i.e., graphite, silicon) materials havebeen thoroughly studied, while the utilisation of the anions in the electrolyte has mostly been overlooked.

The anion intercalates into graphite by chemical or electrochemical means was
first proposed for batteries by Rüdorff and Hofmann in 1938. However, the anion
intercalation brought serious safety issues that hindered its development, due to the
high concentration of acid solution as the electrolyte.

It wasn’t until the 1990s and the mass commercialization of lithium ion batteries
that research and development began in earnest into the application of anion
intercalated graphite as positive electrode in batteries by replacing acid solution
as the electrolyte with room temperature ionic liquids as electrolyte.

Since the 1990s, ongoing investigations have been realized into anion intercalated graphite based dual carbon batteries, such as the investigation of and systematic study of the intercalation of different anions into graphite.

However, due to electrolyte decomposition caused by the high positive potential of anion intercalated graphite (≈5 V vs Li/Li+) and exfoliation of graphite layers upon repeated ion/solvent molecule intercalation/deintercalation, reported dual-carbon batteries showed unsatisfied charge–discharge reversibility.

The Technology
Aluminum Graphite Dual ion Battery (AGDiB)

The benefits of our AGDiB are reduced weight, volume, and fabrication cost,
as well as higher energy density in comparison with traditional LIBs. AGDiB’s
electrode materials are composed of environmentally friendly, low cost
aluminium and graphite, while its electrolyte is composed of conventional
lithium salt and carbonate solvent.

Upon charging, anions in the electrolyte intercalate into the graphite cathode,
while the Li+ ions in the electrolyte deposit onto the aluminum counter
electrode to form an Al-Li alloy. The discharge process is the reverse of the
charging process, where both anions and Li+ ions diffuse back into the electrolyte.

Since the Al counter electrode in the AGDiB acts as the anode and the current
collector at the same time, the dead load and dead volume of the AGDiB is
significantly reduced, making a battery with both high specific energy density
and high volume energy density.

In its research, our team roughly estimated the specific energy density and
power density of the AGDiB according to the configuration of the packaged
battery. Results show that the AGDiB can deliver a specific energy density
of ~222 Wh kg-1 at a power density of 132 W kg-1, and ~150 Wh kg-1 at 1200
W kg-1. Compared with commercial LIB (~200 Wh kg-1 at 50 W kg-1,
and ~100 Wh kg-1 at 1000 W kg-1) and electrochemical capacitors
(~5 Wh kg-1 at 5000 W kg-1), the AGDiB showed significantly
improved performance.

Importantly, the volume energy density of the AGDiB can reach ~560Wh/L
which is much higher than traditional batteries (~350 Wh/L for Tesla Model S
and ~200 Wh/L for BYD E6). For example, a 500 kg, AGDiB-based power
battery could reach a recharge mileage of ~550 km (~425 km for Tesla Model S
and ~225 km for BYD E6), and a 200 L AGDiB-based power battery
could reach a mileage of about 560 km.

Compared with conventional LIBs, this battery (AGDiB) shows an obvious advantage in production cost (~ 50 percent lower), specific density (~1.3-2.0 times), and energy density (~1.6-2.8 times). This discovery is particularly important given rising battery demand and existing LIB technology, which is reaching its limit in specific energy (by weight) and energy density (by volume).

In summary, we have developed a novel AGDiB composed of only environmentally friendly low-cost materials and a specially designed carbonate electrolyte.

The AGDiB shows significantly reduced dead load and dead volume. The AGDiB delivers a reversible capacity of 104 mAh g−1 (based on the mass of graphite) at 2 C current rate, and a capacity retention of 88% after 200 cycles. A packaged AGDiB cell is estimated to delivery an energy density of ≈220 Wh kg−1 at a power density of ≈130 W kg−1, and ≈150 Wh kg−1 at ≈1200 W kg−1, which are significantly higher than most commercial lithium ion batteries, and a world leading low-cost power source with both high energy density and high power density.