I like NiCds, have little use for NiMH, and really like lithium polymer over lithium ion, lithium ferrite or 123A cells. NICds and NIMH do have a memory effect and if they are subjected to an input current at a medium or high charge state, the cell structure crystallizes. Li-Po cells offer about 50% higher capacity than Li-Ion and are capable of much higher currents. The self discharge rate is low, and after sitting at a half charged state for twelve months, I've found Li-Po cells typically lose but a mere couple milliamp hours of capacity per 1kmAh. They do not have the memory effect but do need special care. Some should be cycled at a low discharge rate for the first few cycles, dependent on the brand's cell structure chemistry for proper forming. That in hand, many others have been tested to offer no immediate or long term benefit from cycling. If a lithium cells is left at a high charged state for extended time, it can lead to cell degradation and break down of the conductive nano cell pathway structure. Similarly, over-discharging reduces energy storage capabilities and prematurely increases the cell's IR value. The charge process must be handled by a charger with the proper CV and CC programming that tapers the current toward the end of the charge and prevents the voltage from rising. Most non-computerized type chargers do a poor job and eventually lead to the destruction of the cells. Discharging at too high of a rate can cause them to swell and sometimes burst into flames, vs NiCd which explode but normally do not cause a fire. Newer high end lithium polymer cells can be charged at up to a 10C rate, and can supply several hundred amps from a relatively small package. I can charge some of my Li-Pos in 15 minutes, vs hours for NiMH to take a quality charge. The IR value will increase on its own, offering a maximum performance life window of about two years, afterwhich the voltage drop and useable capacity will be reduced by a notable margin. They are also temperature sensitive and the IR varies are much as 150% with an 8 degree temperature rise. They prefer lower ambient temperatures for storage. It's a good practice to leave 20% of the cells total capacity unused to extend the working lifespan, but in some electronics its not possible to identify the mAh used so the 3.0V/cell rule is used.
Most consumer lithium cells today are overpriced for their decade old performance criteria. Only a handful or manufacturers produce the cells to their client's specifications, they are then re-branded and sold under those names. The performance can vary widely from one chemistry specification to another for each brand. The cells with the cheapest chemistry and conductor pathway are the most common ones found on the market for consumer electronics.
Below is a test I performed a couple years ago on a single cell 250mAh 3.7V lithium polymer cell with a PC logic controlled load, precision is 1/000th of an Ampere and FFT math display. Cell was charged to a normal 4.199V, discharged at 0.990-1.000A and ended at 3.325V. Notice the temperature started at 20.5 degrees Celsius and arose to 30 degrees, yet the discharge rate was only 4C. The voltage drop is typical of a low cost cell as often found in consumer electronics and tools.
This is an 850mAh 3 cell 11.1V pack, tested from 12.6V fully charged and then discharged at 1.990-2.000A to 9.9V/3.3V per cell.
This pack performed good at even 15A and was half discharged about forty times, staying above 3.0V cell until over 90% capacity was depleted in final testing. No memory effect present. Newer packs of this size can provide 60A under the same circumstances.
Sincerely and Best Wishes On your Audio Journey,