IMO most of battery cell energy density advancements of recent years have been due to substantial improvements to the cathode chemistry rather than to the traditional graphite anode chemistry (372 mah/g max theoritical specific capacity VS lithium Nickel Cobalt Aluminum cathodes with usable capacity of only 10mah/g) in other words, way to go before reaching the theoritical capacity at the cell level using graphite anodes.
this is an interesting article explaining why replacing graphite by silicon in the anodes wont result in 10times better energy density of the cell due to the limitations of the cathode chemistry. IMO if we add to this academic discussion, the fact that graphite anodes are relatively cheap and easily mass produced compared to other new promising/competing anode materials for lithum ion batteries, I think spherical graphite have good days (at least 5 years - 10 years) before it gets replaced by another material.
For the past two decades, significant efforts have been dedicated towards the development of high energy density LIBs1,2,3. The energy density of a LIB depends primarily on the specific capacities of cathode and anode, and the operating voltage window at which the battery can be cycled1,2,3. Si has emerged as one of the promising anode materials for high energy LIBs4,5. It is believed that a small amount of Si based material is currently used in the anode of LIBs6. Si offers a suitable low voltage for an anode and a high theoretical specific capacity of ~4,200 mAh/g based on the formation of the Li22Si5 alloy, which is about 10 times higher than that of conventional carbon based anodes (~372 mAh/g)4.
Today, the LIB capacity is limited by the capacity of cathode rather than the capacity of the anode1 with the implication that any gains on anode capacity are proportionately reduced based on the overall cell composition. Commonly used cathodes such as lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), and lithium nickel cobalt aluminum oxide (NCA) have usable capacities of 140 mAh/g, 170 mAh/g, and 185 mAh/g, respectively, which are lower than the widely used graphite anode (experimental capacity: ~330 mAh/g)7. Thus, despite Si having a significantly larger capacity than graphite, the level of improvement in gravimetric energy density on a cell level achieved using Si anode and existing cathodes is limited to a maximum of ~41% (see Fig. S1a). This calculation does not take into account the issue of swelling; when mechanical effects are taken into account, the possible capacity improvement becomes significantly less.
