Batteries are or would be needed for other applications as well, and at high currents a huge number of cycles would be potentially downright revolutionary. For example, distributed regulation of the electricity grid, where large batteries would be a significant part of the regulation, spread over a wide area of the grid.
Nah, we do exactly that, and the trend is the opposite to what you think it is - towards larger capacity, more energy, not so much power in comparison. While there is some need for high speed regulation (currently provided by STATCOMs, inertia and yes, to some extent, by batteries), the power and especially energy involved in the fast regulation loop is rather small. This is because in a grid, short-term effects average out. What happens at minute scale is just noise. But what happens at 15-minute, 1-hour, 1-day scale is far from noise, it shows large trends as function of prediction errors, maintenance, weather, behavioral patterns.
Like, for example, for PV production, a cloud can suddenly cease the production, but it does not happen everywhere at the same second. But during an hour, it can happen over a large area. That's the interesting timescale.
It is true that need for grid-scale energy storage is increasing (see e.g. Fingrid
https://www.fingridlehti.fi/reservien-tarve-kasvaa-kohisten/ , the image every salesman is showing to their residential to-be-customers to sell them our, or our competitor's box; ours is the best of course
), but that increase is almost solely in mFRR (which none of the home battery reserve providers do, we neither), spot energy trading and intraday energy trading. All of which are high-energy, slow assets with large capacity requirement and not that much C-rate involved.
The large need for aFRR, mFRR, intraday energy arises from prediction errors especially in wind forecasts which are done day before for spot markets. Say, e.g. in such small country as Finland, you predicted 4GW of wind and you got 3GW or 5GW. Or, you predicted that the wind ramps down at 7:00AM but it does so already at 6:30AM. So now you would be discharging 1GW for 30 minutes, then afterwards slowly recharging.
While I mention Finland, the same physical reality, and same or similar markets are of course in larger grids, e.g. the Continental Europe Synchronous Area which is a huge grid.
These hour-scale effects are large and energy-heavy. So any large battery asset would be multimarket-optimized, combining whatever balancing periods are most profitable (i.e., most needed). And the typical battery of today is rated to 0.5C or at max 1C, and battery design is not the limiting factor at all, we could well have 2C capable grid batteries already with LFP or Na-ion but
we don't usually need that rating.
And as such a battery traded optimally to all these markets could maybe see 10-20 "cycles" during a day, but those cycles would be with small DOD% so the wear would not be equivalent even of 1 full cycle. Or, in a different market situation even more energy would be needed (e.g., trading energy between night and day), so the cycle would be larger, but then it's also fewer cycles.
So a typical use case for a grid battery could be 1 nearly full cycle for a day plus a dozen of microcycles during the day.
For this we currently use LFP mostly and it already does great job, and financials seem to work out. Only small % is in the cost of the cells, and that is, we are taking the whole lifetime into account.
So, maybe, if we could increase the nominal full-cycle life rating of a typical LFP cell, say, from 3000-5000 cycles to 10000 cycles, it would be nice I guess, but I have hard time imagining other than niche needs for a 10C, 100000-cycle battery, including grid and behind-the-meter balancing/optimization, because a 2C battery 5 times larger, or 1C battery 10 times larger does the same power,
and much more.
This is basically the same discussion as in 2010 when many experts were certain that all we need are 15-20kWh EV batteries that charge at 10-20C, and it was actually quite innovative from early Tesla to show a proof-of-concept that what we actually need is more capacity, and high charge power then comes as an extra, even with lower C rate.
The same is true in power system / grid balancing, we need more and more capacity, and once we have that, the short-term power just comes for free, and does not wear out the battery, because the depth-of-cycle for those short peaks is so tiny.
Conclusion: for mobility, energy density AND price / kWh over the lifetime are still the most relevant. For stationary, price / kWh over the lifetime, not so much energy density.
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