Digital battery

1 Introduction

 

Lithium-ion KD186 NF343 battery is a device very energy efficient and compact storage. Lithium-Ion trend in technology development is the pursuit of superior quality and volume of the specific energy, higher power, and longer service life, cost of ownership, while more the emphasis on adaptability of the machine’s environment and security applications from mobile phones, laptops extended to power tools, light electric vehicles, hybrid electric vehicles, telecommunications prepare electricity, l ‘Aeronautics and space to other areas. The safety of lithium-ion has been the industry and the community aspect of the research. The solutions include [1]: designing the physical structure of the battery safety, using a higher thermal stability of electrode materials, using organic additives or inorganic electrolyte, divide the three levels or composite organic / inorganic (ceramic) composite structure [2], change the traditional electrode materials for oxidation-reduction of organic matter, free radical reactions [3].

 

From a security problem occurs to see the mechanism of chemical reaction, select the electrochemical and thermal stability of lithium-ion battery electrode materials is to prevent abuse of batteries led to security problems the most elementary and middle most important. LiNi0.5Mn0.5O2 high-capacity cathode material and LiNi1/3Co1/3Mn1/3O2-based nickel and cobalt-manganese ternary layered material (patent 3M) less LiCoO2 safety have been greatly improved, but these oxides La thermal stability is not satisfactory. ThinkPad R40 battery ThinkPad X60 battery To LiFePO4 structuring represented by polyanionic phosphate materials because of their outstanding intrinsic safety, life cycle length, the wide electrochemical window, low cost and other characteristics [4] has been examined closely. Phosphate also include materials with high oxidation-reduction of a compound intercalation of electrons as LiMnPO4 [5-7], LiVPO4F [8-10], LiCoPO4 [11, 12], LiNiPO4 [11] , and features high electrochemical capacity of multi-electron Redox intercalation compound, such as Li2NaV2 (PO4) 3 [13] and Li3V2 (PO4) 3 [14, 15]. This article focuses on the most mature of phosphate - the material of lithium iron phosphate, the latest research and progress of industrialization.

 

2 Lithium Iron Phosphate inherent structure, physical properties and application of the barrier

 

LiFePO4 olivine structure is a polyanionic phosphate PO bond is very strong materials, thermodynamic stability, the use of safe and reliable, is currently the most talked about one of the subjects of the lithium-ion battery cathode . The material is completely incapable of electrochemical intercalation of lithium, the network, b axis contracted by 5% and 3.6%, c-axis direction of elongation of 2%, the size of the bias network smaller, about 6.6%, the lattice strain is low, material structural stability, life cycle very long. LiFePO4 has also a non-toxic, hp Pavilion dv8000 battery  hp Pavilion dv4 battery environmentally friendly, rich in raw materials capacity (theoretical capacity of 169 mAh / g platform) and the coulomb efficiency is high and stable, loading and unloading (3.45 V Li vs. / Li +), high energy and the specific benefits of specific power, if the material is appropriate for safety, cycle life, power characteristics, such as the use of cost-sensitive applications to battery scale.

 

LiFePO4 charge and discharge process can be broadly described as: LiFePO4FePO4 Li + + + E. At room temperature, the behavior of LiFePO4 lithium intercalation de-FePO4 training and is actually a dual interface LiFePO4 phase two process reaction phase [4]. Newman [16] Yamada [17], Dodd [18] respectively, a systematic study of the process of loading and unloading process LixFePO4 phase transition (see Figure 1).

 

LixFePO4 is a typical mixed ionic conductor electronic bandgap of 0.3 eV, the electronic conductivity of the ambient temperature is very low, about 10-9S/cm; LixFePO4 room temperature ionic conductivity is very low (~ 10-5S / cm), the characteristics of olive stone construction makes the body of the Proliferation of lithium-ion F4809A F4812A channels (only reach the quasi-one-dimensional diffusion), the LixFePO4 off a reaction in two phases lithium intercalation, LiFePO4 FePO4 and theoretical lithium-ion the diffusion coefficient of around 10-8 cm2 / s, and 10-7 cm2 / s [19], while the actual measure of LiFePO4 lithium-ion and FePO4 the “effective” diffusion coefficient may be lower than the theoretical value of 7 orders of magnitude, respectively, 1.8 × 10-14 cm2 / s and 2 × 10-16 cm2 / s [20]. So, make LiFePO4 for lithium-ion battery cathode material must also improve their electronic conductivity and ionic conductivity, improving its capabilities electrochemical interface.

 

3 Material Lithium iron phosphate method modified

 

On lithium iron phosphate to improve the electrical conductivity of the main methods include: granular nano-technology; coated conductive layers, such as nano-carbon layer, the right to conduct body doped lithium iron phosphate, synthetic material Lithium Iron phosphate in the surface of a good electronic conductivity Fe2P, and Fe3P phase Fe15P3C2, improving materials of lithium iron phosphate, the surface morphology, as Valence Technology Inc. has proposed a (CTR carbothermic Reduction ) method [21] will be conductive carbon particles dispersed in phosphate. Nano particle materials lithium-ion battery is to improve the conductivity of the most commonly used. Lithium PA3421U-1BRS PA3591U-1BRS iron phosphate, reducing the particle size and shorten the effective diffusion of lithium ions travel, can effectively improve the ionic conductivity of the material. Granular materials, nano-technology will reduce the electronic conductivity, it is usually also the introduction of synthetic materials, the doping of metal ions and conductive material coated on the other hand, carbon coated in situ, particular can effectively control carbon coated lithium iron phosphate materials, nano-size particles. Material lithium iron phosphate synthesis itself, we are often several methods used in the same time, the role of co-existence of several mechanisms.

 

Changing the doping is to improve the functional electrical properties of electron transport and electric or ion to improve the structural stability of materials, the most common. Lithium iron phosphate is often used to driving on the mass of doped metal ions, including Mg2 +, Ni2 +, Co2 +, Al3 +, Ti4 +, Zr 4 +, Nb5 +, W6 +, etc. [21-24]. Chunsheng Wang et al [22] The study showed (see Table 1), doped with magnesium can significantly improve the electronic conductivity of lithium iron phosphate, and a modest increase in ionic conductance, the combined effect of the electronic conductivity and ionic conductivity in the same order of magnitude, the electron-doped A1022 A1185 Neither the rate of increase in conductivity is dominant, but the ionic conductivity is virtually unchanged, at 25 ℃, LiFe0.95Mg0.05PO4 magnification feature much better than LiFe0.95Ni0.05PO4. Nian 2002 MIT Materials Science Department of Chiang YM research group reported the results of attention [24], the study found that the material of lithium iron phosphate doped with Nb5 + and other metal ions in the 4a position of Li hole generated after the carrier, the conductivity of materials increased to 3 × 10-3 ~ 4 × 10-2 S / cm, even more than the LiCoO2 cathode materials oxides (~ 10-3 S / cm) and LiMn2O4 (~ 10 -5 S / cm) conductivity.

 

However, Chiang YM concluded there is considerable controversy, including: doping can significantly improve the electronic conductivity of the material but, in fact, this period of conductivity of materials, measures may be lithium-ion diffusivity and ionic conductivity, nano-technology to reduce the lithium-ion diffusion May be difficult to explain the phenomenon of text, such a substantial increase in electronic conductivity of this material may not be boosted by the formation of Li1-xNbxFePO4 “but is another conductive material and a better ability to generate income. Nazar et al [25] that the iron phosphate lithium material body does not significantly improve the conductivity caused by doping, but because the synthesis process, particularly in high temperatures, easy-phosphate formed on the surface such as Fe2P conductive metal phosphides such as nano-network caused by network operators to improve the conductivity of grain boundaries phosphate. TravelMate 290 battery BATBL50L6 Prosine, etc. [26] found that non-doped nano-or sub-micron (100 ~ 150nm) Supports Lithium iron phosphate 3C flow below the same time have a good zoom feature. Masquelie etc. [27] found that even without doping, uncoated carbon, particle size about 140 nm in lithium iron phosphate below 5C discharge rate is 147mAh / g capacity of specific high They also believe that [28] simply can not be Nb-doped lithium iron phosphate is generated in the so-called “Li1-xNbxFePO4″ materials to improve electronic conductivity of lithium iron phosphate to improve its performance electrochemical mainly attributed to NbOPO4 and / or (Nb, Fe, C, O, P) network of driver training. In fact, in 2001, Yamada et al [29] had already proposed to reduce the particle size material is overcome Lithium iron phosphate Lithium-Ion scattering effectively the problem is limited. YM Chiang and so on in recent years have begun to focus on nanoparticles of lithium iron phosphate end of a study (the United States Patent Application: US2007/0031732A1 and US2007/0190418A1).

 

Carbon in iron phosphate coating of lithium material is also to improve the performance of the most commonly used modified carbon coating of lithium iron phosphate can not only improve the electronic conductivity of materials, but also can effectively control the particles of iron phosphate lithium in grain growth, is to obtain nano-particles, improve the capacity of lithium-ion diffusion of effective ways. University of Montréal, Hydro-Quebec Research Institute and the University of Texas Goodenough carbon in organic carbon coated group conducted a series of effective methods of research, and its greatest impact. In 1999, Ravet, Goodenough and et al [30] first proposed organic compounds (sucrose) as a carbon source for the lithium iron phosphate material in-situ modified carbon-coated, was found at a high temperature 1% of carbonaceous materials, lithium iron phosphate of the 1C discharge capacity of the microscope up to 160 mAh / g was close to the theoretical capacity, which is better than Padhi, and Goodenough [4] in 1997 reported the results of a new qualitative leap since become the modified carbon, iron phosphate coated Lithium is one of the methods most important change. In 2001, PCGA-AC16V6 PCGAAC19V3 Nazar et al [31] a combination of carbon coated, and the concept of nano-particles, the first truly shows the carbon-layer nano-or sub-micron scale, lithium iron phosphate has a very characteristic high magnification (magnification 5C, the maximum capacity 120mAh / g), the results show that carbon-coated lithium iron phosphate can also improve the electronic conductivity and ionic conductivity. Nazar, etc., but not the carbon content and particle size of lithium iron phosphate is optimized, and takes into account the volume ratio of materials, energy issues (carbon content of the text up 15%, will significantly reduce the density of matter from the tap). Dahn et al [32], then try a variety of ways carbon coated to reduce expectations of LiFePO4 / C composite electrode of carbon to improve the overall quality of the material energy, the ratio of the volume and energy tap density, they stressed that the right to lead iron phosphate coated carbon amendment must be comprehensive review of synthetic materials and preparedness capacities, capacity expansion, and the tap density effects. In 2003, Valencia in Baker et al [21] reported the use of “carbon thermal reduction (CTR-carbothermal Reduction) Preparation of coated carbon (carbon modified formulation May be more appropriate) and iron materials phosphate lithium, methods dihydrogen oxide, lithium iron as main raw material, carbon as reducing agent and carbon source, carbon thermal reduction method using the synthetic material and the discharge capacity up to 156 mAh / g ; The synthetic method is a notable feature of the synthesis of matter incorporation of metal ions, while the carbon can be dispersed in tiny particles, while diffusion in the secondary particles, the conductivity of materials is very good . Valencia provided product information to see, the CTR is not only, as mentioned in the text is probably the best way to achieve industrialization, also appears to be integrated optimization of materials, capacity, capacity of ‘expansion and tap density of the ideal way. apple iBook G4 12 inch battery apple iBook G4 14 inch battery