Is LM35 Accurate and Reliable for Battery Temperature Sensing Applications?

Please help me asap

Yes, I believe so. LM35 is a common temperature sensor and is already calibrated in °C. Do you intend to use it on rechargeable batteries? I think it's better to use a thermistor. Aside that it's cheaper, it covers wider temperature range than LM35 and works at any voltage. Also, thermistors are known for its precise temperature measurement.

Advantage of lm35 is that it is calibrated directly in degrees celsius, with a known linearity as well.
A thermistor normally needs a look up table on a processor to linearize it, although it can be done in the analogue domain, if the temperature range is low enough it doesn't take too much work. Either way, you have to calibrate it if you need to know the temperature absolutely, crushed ice in water, and boiling water will give you two points, but over that range linearity will suffer,
cheers,
Richard

When using a temp sensor like this it is a good idea to use 2 of them, one at ambient and one at battery temperature. Use a comparator so that if battery temp is much greater than ambient then stop the charge. You'd need a bit of hysteresis to do this - an op amp will do it for you. This way you'll avoid false charge stopping in hot environments or overcharging in cold ones.

For what it's worth the LM34 provides two advantages over the LM35. Since it is in Fahrenheit, sensitivity of the LM34 is approximately double that of the LM35. Secondly if you look at the "Basic" configuration (on the first page of the data sheet), the LM34 will operate down to 5 degF (-15 deg C) as opposed to the basic configuration of the LM35 which is only rated at 2 degC.

Since it is probably unlikely that your battery is going to work in a negative environment it probably doesn't matter.