So many problems here
"Instead, about 80 per cent of respondents estimated that between 10 and 50 per cent of the capacity of the battery systems deployed in their data centre today is excess..."
First of all, 10% is not a lot of margin. Battery capacity varies with temperature and age and most battery banks at DCs are designed to last only long enough to start generators; 10% of that time is not much. 50%, on the other hand, is a lot of excess margin, but either it was specified that way for good reason (to survive a 99th percentile generator startup time instead of 95th, say) or it should never have been designed that way in the first place and is a waste of money. In short, there should not be "excess capacity" in DC UPS battery banks.
"According to Schneider Electric, these changes have been made possible by newer UPS systems using lithium-ion battery technology rather than the valve regulated lead-acid (VRLA) batteries traditionally used."
This is both true and a lie. Flooded lead-acid (same chemistry, different maintenance design) is no more expensive than VRLA but with proper maintenance -- which can be partially automated -- have design lifetimes up to 5000 charging cycles. There are two basic parameters that affect lead-acid battery lifetime at a given depth of discharge: plate thickness and electrolyte maintenance. VRLA batteries "wear out" because they lose electrolyte during charging and it's not replaced. The valves regulate this loss but do not eliminate it. Because of this limitation, they are also designed with thin plates because there is no point in having plates that will outlast the electrolyte. Thinner plates also allow greater current to be supplied by the cell, which is important for applications like starting an engine, but for UPS applications even very thick plates can supply more than adequate current. Flooded batteries have no valves but are designed to have water added periodically to maintain proper electrolyte levels. They can be, and are, designed for a wide range of points on the curve of cost and max current vs. lifetime and depth of discharge. This is the main distinction in whether the batteries you see at the auto shop are being sold as "starter", "deep-cycle marine", "off-grid power", etc. Installing thin-plate VRLA batteries in a stationary application like a DC where weight poses no problem and a staff is always on site to perform periodic maintenance is insane. A DC UPS battery bank will have a very small number of very deep discharge cycles and will otherwise be maintained at the float voltage, which means electrolyte loss will be minimal. Whether FLA or VRLA, such a bank should have a lifetime of 7-10 years minimum and possibly longer. There are many batteries on the market today with these attributes and warranties of 7 years or more. Lithium-ion is much lighter and more compact -- important for mobile applications but unimportant for stationary use -- and is maintenance-free, but it is also 3-10x as expensive at a given capacity point and comes with a small risk of causing a fire that is all but impossible to extinguish. The only reason to push for lithium chemistries in an application like a DC is because you're selling ignorance. If your goal is to market your DC to people who think lead-acid is "obsolete" and lithium the new hotness, by all means. Or if you're a manufacturer of lithium-based batteries and can convince a DC manager of that on the golf course, again bully for you. Otherwise it's a joke.
'"In addition to voltage and frequency regulation plus power back-up, a data centre UPS can be used for peak shaving, demand response, and even to send excess power into the utility grid for profit," he said.'
Yes, and the equipment suppliers listed have been selling electrical equipment for many years that offers all of those features and support a wide range of battery chemistries, voltages, and capacities. All of this has been on the market for over 20 years and has been widely-deployed with mostly FLA or VRLA battery banks. This feels like nothing but a marketing push: talk up "renewable energy grid integration" and "new frontiers opened by lithium-ion batteries" because those things sound sexy and people read about them in newspapers; maybe it'll sell more electrical gear. In fact there's nothing new about any of this; you could (and many have) built systems that do all of this in a dizzying array of scales, applications, prime power sources, and grid integration or lack thereof. There's no good reason to add these features to a DC UPS unless the DC is powered mainly by local generating sources rather than the grid, in which case the UPS is not really a UPS any longer but a core part of the electrical supply system with very different design goals.