**Abstract**

As electric vehicle market growing fast, lithium ion batteries demand is increasing rapidly. Sufficient battery materials supplies including cathode, anode, electrolyte, additives, et al. are required accordingly. Although layered cathode is welcome in high energy density batteries, it is challenging to balance the high energy density and safety beside cost. As consequence, olivine phosphate cathode is coming to the stage center again along with battery technology development. It is important and necessary to revisit the olivine phosphate cathode to understand and support the development of electric vehicles utilized lithium ion batteries. In addition, blend cathode is a good strategy to tailor and balance cathode property and performance. In this chapter, blend cathode using olivine phosphate cathode will be discussed as well as olivine phosphate cathode.

**Keywords:** phosphate, phosphate composite, blend cathode, lithium ion battery, electric vehicles, stability, rate capability, safety

### **1. Introduction**

Batteries are used as the power source in electric vehicles and take the critical role for driving milage improvement and transportation safety as well as cost control. Battery energy density is the important parameter related with the driving mileage. As battery material and technology development, energy density of lithium ion battery for electric vehicle has been increased to 300 Wh/kg at cell level, [1, 2] it has big progress compared with the lead acid battery at beginning period. Lithium ion battery is basically composed by cathode, anode, separator and electrolyte. Lithium ions move between cathode and anode to store and output energy through reversible chemical reaction. In present commercial lithium ion batteries, lithium ions are reserved in cathode side and the reversible lithium concentration in cathode mainly determine the battery energy density. Three type of cathodes have been widely utilized in commercial lithium ion batteries, layered oxide which has two-dimensional lithium ion diffusion pathway, spinel oxide that provides three-dimensional lithium ion transportation space, and olivine phosphate with one-dimensional lithium ion diffusion channels. Each of them has their merit and are servicing the specialized portable power source market.

Lithium ion battery utilized on electrical vehicles has high requirement on safety, long lifespan, high energy density, high power density as well as low cost. Olivine phosphate cathode has stable crystal structure and present advantage on safety, long cycling stability and cost effective. In this chapter, lithium iron phosphate, lithium manganese phosphate and related composite cathodes are reviewed to understand material technology development. Blend cathode demonstrates the possibility to tailor and balance the cathode property and performance. Binary and ternary blend cathodes using olivine phosphate are summarized and discussed.
