| The development of lithium ion power batteries was reviewed in detail. The dependence of electrochemical properties on the microstructure, morphology of anode and cathode materials were comprehensively investigated, and then the key materials for power lithium ion batteries were selected. Several kinds of advanced electrolyte for power batteries were developed. A series of manufacture technologies, such as the optimization of battery structure design, the improvement of safety were achieved. And then lithium ion battery with high energy density and that with high power density were developed. The thermal behaviors of the batteries during charge/discharge were studied, and the model of surface temperature distribution and thermal dissipation were established. The electrochemical properties and safety performances of the batteries were characterized. Finally, the pilot-scale manufacture of high energy density battery and high power density battery were carried out.1. Lithium ion batteries with high power density were developed. LiFe1-xMgxPO4 cathode materials were synthesized by solid-state reaction. According to the results of cathode material characterization, the substitution of Fe with Mg in the LiFePO4 lattice has caused the contraction of unit cell volume and the decrease of lattice parameter a, b, as well as the improvement of electron conductivity. The prepared cathode material LP3, with stoichiometry of LiFe0.95Mgo.osPO4, Characterized with smooth surface and spherical morphology, has relatively concentrated particle size distribution(median size 7μm) and exhibits excellent electrochemical and high power properties. The MCMB (Mesophase Carbon Micro-Beads) samples shows a low specific surface area, narrow particle size distribution, stable cycle property and can be charged/discharged in a large current, which qualifies it to be the anode active material of lithium ion batteries with high power density. And then the lithium ion batteries with high power density were developed. The lithium ion batteries with high power density exhibit excellent electrochemical properties. The capacity retention ratio remains 87% after 1900 cycles. Compared with the discharge capacity at 1C current rate and ambient temperature, the discharge capacity at 30C current rate remains 91% and that at-20℃remains 62%, respectively.2. Synthesis and study of the high energy battery. The results of cathode material characterization indicate that the spinel LiMn2O4, characterized with lattice parameter a<8.21 A, exhibits smooth surface, perfect crystal growth, specific surface area below 1.0m2·g-1 stable structure and well particle size distribution. The John-Teller effect and the undesired reaction between LiMn2O4 and electrolyte decrease. Therefore, the material with typical properties described above is selected as cathode active material for the high energy battery.The advanced electrolyte special for LiMn2O4 power battery was studied. The swell rate of the battery decreases from 35.11% to 12.40% when 3% 1,3-PS and 5%PC used as electrolyte additives. For 0.1M LiBOB mixed with LiPF6 battery, the cycle life of LiMn2O4 power battery is greatly improved about 3 times at 60℃.The safety performance of LiMn2O4 power battery was also investigated. It is found that the addition of 2% CHB will improve the battery overcharge property. The LiMn2O4 battery passed the 3C/10V overcharge without any other expense. The SEM and FTIR characterizations show that the action mechanism of CHB was as ascribed to interdiction with.The capacity retention of the manufactured battery is 86% after 500 cycles, at 0.5C rate. The discharge capacity of the battery retains 86% at 20C, compared to that of 1C. The relatively high temperature (55℃) has little effect on the discharge capacity. However, the capacity retention is only 75% at low temperature (-25℃)..3. The potential factors contributing to the heat production were comprehensively concluded. The dates were collected from the surface temperature of LiFePO4 power battery (Model:F11100120, Nominal Capacity:10Ah, Nominal Voltage:3.2V) discharging at 3C rate, and analysed by fitting soft. The fitting model of temperature distribution of battery is as follow: t= a+bx+cx2+dx3+ex4+fx5+gy+hy2+iy3+jy4+ky5(x, y is the width and length of battery respectively, and the indexes of x, y are constant, t is temperature)The heat dissipation model was also established as follow: Q1=4Qf+2Qs+2Qa+2Qb(Qt is total thermal dissipation, Qf is obverse surface thermal dissipation, Qs, Qa, Qb denote the left and right side, the front side, the rear side thermal dissipation respectively)The safety testing items, including overcharge, overdischarge, short circuit, nail penetration, crush, heating test, were performed according the method of Industry Standard QC/T 743-2006 "Lithium-ion batteries for electric vehicle". All the testing items are satisfied.4. The pilot tests of high energy density battery M95100170 (13Ah) and high power density battery F11100120(10Ah)were carried out respectively. Key-point controls were performed on the safety and consistency technology. The results of pilot product show that the yield of M95100170 and F11100120 is 97.2%,95.2%, respectively. The consistency of pilot product is fairly good. The specific energy density of M95100170 is 151Wh-kg"1 or 330Wh-L"'and the specific power density of F11100120 is 2100W-kg"1, or 4000W-L"1. Both pilot products are in the advanced level, comparing with similar products at international. Furthermore, lithium power battery packs (13 Ah/36V) were assembled with M95100170 cell in series. The capacity retention rate of pack is 82% after 500 cycles. The pack also passed all the safety testing items according the method of Industry Standard QC/T 743-2006 "Lithium-ion batteries for electric vehicle".
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