Batteries: Lithium Ion VS Lithium Sulphur

(good to know, Cut&paste from here)

Conventional lithium-ion batteries are reaching their theoretical maximum gravimetric energy density of just 387Wh/Kg.

A major EV battery supplier in the market has reported that their best batteries currently deliver 260Wh/Kg, with a forecasted improvement of just 20% over the next 5 years.

Lithium-sulphur batteries have a theoretical gravimetric energy density of 2,567 Wh/Kg – in the order of 5x that of lithium-ion batteries.

A battery with a higher gravimetric energy density will last longer before needing to be recharged, which should enable EVs to travel farther and drones to fly for longer between recharges.

Lithium-ion batteries rely on heavy metals such as cobalt, manganese and nickel in the cathode. As a result, lithium-ion batteries can be up to 3 times heavier than equivalent energy lithium-sulphur batteries.

The lithium, sulphur and carbon used in lithium-sulphur batteries are much lighter than the heavy metal oxides used in lithium-ion batteries. The greater gravimetric energy density of lithium-sulphur batteries compared to lithium-ion batteries facilitates a lighter batteryfor the same energy stored.

Lighter batteries are a significant advantage for applications such as wearable devices, EVs, medical devices, drones and aircraft.

Lithium-ion batteries require a range of heavy metal oxides for the cathode that include cobalt, nickel and manganese.

These heavy metal oxides are expensive, representing up to 34% of the total battery cost with volatile market pricing. For example, 70% of the global supply of cobalt is sourced from the geopolitically unstable Democratic Republic of the Congo. This creates an ongoing supply risk and potential cost risk.

Sulphur is an abundant element in the Earth’s crust and is often created as a discarded by-product of other industrial processes. It costs less than 1% the cost of lithium cobalt oxide (the material predominantly used in the cathodes of lithium-ion batteries).

The low mass of lithium metal needed for a lithium-sulphur battery anode also keeps production costs down.

These lower component costs, when compared to lithium-ion, assist with mitigating the cost of BNNTs used to provide the improved cycling stability of Li-S Energy Battery cells.

Charge rate is governed by charge rate capacity. Lithium-ion batteries have a lower charge rate capacity, which means fast charging causes rapid heating and cell degradation. This limits the safe charging rate, creating an issue for all applications that require rapid charging, such as for drones and EVs.

Lithium-sulphur batteries have a higher charge rate capacity and can be recharged faster due to their chemical design. The higher energy density also delivers more energy per charge/ discharge cycle, leading to fewer charges being required.

Lithium-ion batteries have been cited in a number of catastrophic failures, including in mobile phones that have caught fire on a plane, exploded in a phone user’s pocket, and in EVs that have caught fire causing death. Commercial lithium-ion batteries can be prone to “thermal runaway” resulting in these catastrophic failures and fires.

According to the Faraday Institute:

“Lithium-sulfur cells offer significant safety benefits over other battery types due to their operating mechanism. The ‘conversion reaction’, which forms new materials during charge and discharge, eliminates the need to host Li-ions in materials, and reduces the risk of catastrophic failure of batteries. Alongside this, the highly reactive Li anode is passivated with sulfide materials during operation, which further reduces the risk of a dangerous failure. While thermal runaway remains a possibility in Li-S cells, research has shown that the magnitude of this failure is significantly lower than Li-ion cells.” (sic)1

The mining of heavy metals used for lithium-ion batteries causes significant environmental and ecological damage. Cobalt, in particular, is mostly mined in the Democratic Republic of the Congo in central Africa. Discarded lithium-ion batteries can leach heavy metals into landfills and water sources.

Lithium-sulphur batteries do not use heavy metals. Most lithium metal is produced from ore and brine reservoirs. Sulphur is naturally occurring and is available worldwide at low cost and with less environmental impact. While there can be environmental consequences of any form of metal ore mining process, discarded lithium-sulphur batteries do not leach heavy metals into the environment.

Wikipedia: The key issue of Li–S battery is the polysulfide “shuttle” effect that is responsible for the progressive leakage of active material from the cathode resulting in too-low recharge cycles.

In 2022 researchers reported the use of a cathode made from carbon nanofibers. The cathode slowed the movement of polysulfides. Using chemical vapor disposition crystallized the sulfur, turned it into monoclinic λ-Sulfur. This allotrope was not reactive with carbonate electrolyte, thereby avoiding polysulfide formation. The cathode endured 4,000 cycles and offered triple Lion battery capacity.

Interesting note: my electric microcar has a 9KWh li-ion battery, which translates to aprox. 80-90 Km driving range urban driving (maximum 2 passengers, average likley 1.2) maximum speed 70Km/h, so a battery of aprox 35-40Kg

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