digital batteries

1 Introduction

The lithium-ion batteries because of its high voltage, high energy density, long service life, environmental pollution and other advantages of the famous [1, 2], but with the rapid development of technology electronic information, the performance of lithium-ion batteries are also more high demand. As a cathode material for lithium-ion VGP-BPS10A/B PA3451U-1BRS battery at present material is most critical, and its development is also a concern.

The current common cathode materials are lithium-ion battery main layers structure of lithium cobalt oxide, nickel, lithium, lithium manganese spinel and olivine structure of iron phosphate and lithium. Among them, the lithium cobalt oxide (LiCoO2) simple preparation, high load and the discharge voltage, excellent cycling performance and widely applied. However, because of the limited resources of cobalt, high cost, environmental pollution and a greater ability to decrease the resistance to overload, the development of space is limited [3, 4]. Lithium Nickel (LiNiO2) higher capacity, but the preparation time on the formation of non-stoichiometric product of poor structural stability and thermal stability [5]. Lithium manganese oxide spinel LiMn2O4 more, there are layers LiMnO2. Above capacity in which layers LiMnO2, but is metastable thermodynamics, structural instability, there is the Jahn-Teller and poor cycling performance [6]. Spinel LiMn2O4 process is simple, inexpensive, high-voltage discharge, environmental performance friendly security, but less than the capacity, ability worst fading at high temperature [7]. lithium iron phosphate cathode material is relatively new, its safety, low cost, but it is low voltage (3.4V), the tap density low, no mass production and so inadequate . Several shortcomings of cathode materials above are further restricted the application of its own, so look for new cathode materials has become the subject of research. PA3399U-1BAS PA3399U-2BAS

LiCoO2, LiNiO2 with the structure α-NaFeO2, and Ni, Co, Mn adjacent elements in the same period, so they can be mixed in a proportion of the formation of solid solution and maintain the same layered structure, with complementary good structure. At the same time, they complement each other in the electrochemical performance is also very good [8]. Therefore, the development of composite cathode materials for lithium-ion battery cathode became one of the researches. Among them, layered Li-Ni-Co-Mn-O series of materials (called “ternary materials) to achieve the benefits of both three and form their own deficiencies, high specific capacity, low cost, performance and stability of the cycle, better performance characteristics of the security [9-14], is considered preferable to replace LiCoO2 cathode materials. Therefore, the ternary material has become a hot cathode material. Research Recent ternary material was reviewed, analyzed the material system, the existing problems and future research priorities. PA3399U-1BRS PA3399U-2BRS

2, ternary materials, structural characteristics and electrochemical properties

Layered Li-Ni-Co-Mn-O oxide has been proposed by Liu [15], etc. proposed in 1999 can be used as cathode material for lithium-ion batteries. They Co, Mn, Ni LiNiO2 replaced with co-precipitation of the hydroxide LiNi1-yCoxMnyO2 x-series hardware, found that the electrochemical properties of the material are more excellent than LiNiO2. Ternary material system, thus gradually in the field of vision quest.

In the ternary system material, nickel, cobalt, manganese is the same cycle of adjacent elements, and LiCoO2 and LiNiO2 with the structure α-NaFeO2, the ratio can be mixed with any form of solid solution and maintain the same layered structure. The system, the physical properties of the material and electrochemical properties of transition metal elements as the report is amended. The general belief, the presence of Ni lattice parameters c and a larger and thus c / a decreases, increasing the capacity. Ni2 + content is too high, and Li + in the scuffle led to a deterioration in the performance cycle. Co can stabilize the ternary layered material and inhibit the cycling performance mixed cationic and upgrade the electronic conductivity and improved, but the increasing amount of cooperation led to a decrease in A and C and C / A increases, low capacity for change. The presence of Mn can reduce costs and improve structural stability and physical security, but the high Mn content reduced the ability to affect the layer structure of materials. Therefore, the optimum ratio of transition metal elements in the system of matter, the object of study. PA3465U-1BRS Satellite A80 battery

ternary material system, the present study are mainly: LiNi0.5-xCo2xMn0.5-XO2, LiNi1-x-yCoxMnyO2, LiNixCoyMn1-x-Yo2, LiNixCo1-x-yMnyO2, etc., where x, y que smaller doping . Among them, the LiNi0.5-xCo2xMn0.5-XO2 researchers great concern, especially in the first by the [Ohzuku 16] established in 2001, is considered received LiNi1/3Co1/3Mn1/3O2 cathode materials the most promising to replace LiCoO 2. The following example we LiNi1/3Co1/3Mn1/3O2 material structural characteristics of ternary material characteristics and electrochemical reactions in more detail.

2.1 Properties of structural materials ternary

Ohzuku, etc. [17, 18] using the first results show that the principles of calculation, α-LiNi1/3Co1/3Mn1/3O2 NaFeO2 with a single layer structure, the theoretical calculation of lattice parameters a = 2.831? C = 13.884?, and the experimental determination of lattice parameters a = 2.867?, c = 14.346?. little lithium ion layer in the occupied territories 3a-bit, free distribution of transition metal ions in the layer of transition metal 3b, oxygen ions occupy in the total side MO6 (M = Ni, Co and Mn ) gap octahedron 3c bits [19, 20]. Among them, nickel, cobalt, manganese valence is +2, +3, +4, Ni and Mn electronic structure is different and LiNiO2 LiMnO2 Ni, Mn, also, other than LiNi1/3Co1 / 3Mn1 / 3O2 structural stability. acer Aspire 1410 battery acer Aspire 5560 battery

The actual product in the synthesis, Ni, Co and Mn disorder in 3b arranged location, and there are cations stampede. Li + can not exist in the metal layer transition and transition metals Ni2 + radius (0.69 + rNi2?) And Li + radius (0.76 + rLi2?) Close, occupy the layer of lithium 3a position, while Co3 + and Mn4 + less busy 3a position [21-23]. cation disorder at high temperatures is more evident in the reduction of oxygen by the rate of cooling to remove [24]. XRD spectra of the ternary materials, it is generally considered when the (003) / (104) peak intensity ratio exceeds 1.2, and (006) / (012) and (018) / (110) duplication of peaks appeared when the ternary material layer structure is well maintained and blur the small cations, electrochemical properties are excellent.

2.2 Characteristics of the electrochemical reaction of ternary materials acer Aspire 5920 battery acer Aspire 5520 battery

LiNi1/3Co1/3Mn1/3O2 that Ni2 + and Co3 + is completely oxidized to 4 +, its theoretical capacity of 277mAh / g. In the 3.7 ~ 4.6V, between producing Ni2 + / Ni3 + / + and Co3 NI4 + / Co4 + valence change, while Mn is stable for 4 does not participate in redox reactions, stabilization of the structure of the role of load balancing across the network electronic transfer of oxygen to reach [18, 21, 26]. In Li1-xNi1/3Co1/3Mn1/3O2 in, Ni2 + / Ni3 +, Ni3 + / + and Co3 + NI4 / Co4 + redox corresponding to 0 ≤ x ≤ 1 / 3, 1 / 3 ≤ x ≤ 2 / 3 and 2 / 3 ≤ x ≤ 1 range, Ni2 + / + and Co3 + NI4 / Co4 + corresponding voltages were about 3.8 ~ 3.9V and 4.5V [12, 17]. Choi et al [27] study shows that when x ≤ 0.65, O 2 remained unchanged, when x> 0.65 pm, O, the average valence decreased with the oxygen system to escape structure, chemical stability to be destroyed. The results of XRD analysis, x ≤ 0.77, keeping the O3 phase. When x> 0.77, the observed new phase MO2 appear. Thus, while raising the threshold voltage discharge can improve the specific capacity of the material, but its cycling performance significantly.

The temperature, the material that the increase in capacity. Yabuubhi [28] The study found that in the range of 2.5 ~ 4.6V, 30 ℃ under capacity 205mAh / g, 55 ℃ when the capacity is 210mAh / g, while at 75 ℃ 225 mAh / g, and it is good capacity rate. acer TravelMate 220 battery acer TravelMate 240 battery

Between the cathode and the electrolyte 3.2 exothermic

Cathode materials are usually in the charged state is very unstable and easily decompose and release oxygen, the release of oxygen reacts with the electrolyte and generate heat, causing the temperature rise of VGP-BPS11 VGP-BPL11 battery, lead causes more thermal runaway reaction. Wang [35] found that the electrolyte and the thermal stability of the coexistence electrolyte Li0.5CoO2 Li0.5CoO2 system and their thermal stability is even worse, starts to decompose at lower temperatures. Zhang [29] At the start of reaction temperature and the heat of comparison, the best thermal stability was found LixMn2O4, LixCoO2 second LixNiO2 thermal stability of the worst but LixCoO2 LixNiO2 with the electrolyte, and between 200 ~ 230 ℃ their violent exothermic reaction took place, with the x value lower the reaction temperature began to drop, the heat of reaction increases. For LixMn2O4, the value of x the size of the positive reaction with the electrolyte temperature and the heat began almost no effect. Cho [36] reported that the use of coated nanoparticles effectively inhibited LixCoO2 AlPO4 the cathode material and the exothermic reaction between the electrolytes. Wan, Xinhua [37] found that lithium cathode material for Ni, modified by coating can increase the thermal stability of lithium nickel coated thermal stability and thermal stability of lithium cobalt altogether. In [38] The lithium manganese oxide and lithium nickel material coated hybrid (1:1 by weight) as the positive electrode, the study found mixed material has more than Lithium Cobalt better thermal stability. Macneil [39, 40] using an arc and measures PA3176U-1BRS PA3178U-1BRS X-ray diffraction were Li0.5CoO2, responsible Li1.5MnO4 between the cathode and the electrolyte exothermic reaction has been studied. Studies show that the temperature is higher than the decomposition occurs powder Li0.5CoO2 200 ℃, the precipitation of oxygen, while the EC / DEC solvent exothermic reaction at 130 ℃, the solvent after adding LiPF6 inhibition of the reaction. For LiMn2O4 material change to 160 ℃ heat crystal solvent has no effect on this reaction. After the addition of electrolyte LiPF6, with increasing concentration, LiPF6 LiMn2O4 and reaction between the electrolytes increased. On the view that [41], high temperature, the reaction between the electrolyte and are LixCoO2 auto-catalytic reaction, lead directly to a thermal runaway. Jiang [42] found that the high temperature cathode materials prepared LiNi0.1Co0.8Mn0.1O2 beginning with the cathode material as the electrolyte temperature LiCoO2 starting in the same conditions of high temperature at 40 ℃, systems high thermal stability of sex.

3.3 Stability of the electrolyte temperature

When the temperature of the PA3191U-1BAS PA3191U-1BRS battery, the electrolyte in the battery has participated in almost all reactions occur, including not only the electrolyte and anode, cathode and includes the reaction between the decomposition of the electrolyte itself. 250J temperature electrolytic decomposition of general heat above 200 ℃, / g or so [31]. Boot [43] found that reducing the concentration of electrolytes LiPF6 from electrolyte temperature of decomposition reaction heat, the heat of reaction decreases. Concentration in certain circumstances LiPF6, with the lowest concentration of the electrolyte in the CE, EMC increasing concentration of electrolyte on the initial temperature of thermal decomposition, the heat of reaction decreases sharply. They [44] study used the modified response system found screening tools, EC and EMC at 263 ℃ and 320 ℃ start factoring CO2, O2, H2, etc.. Campion [45] studied the LiPF6 formed in different solvents in the thermal decomposition of the electrolyte, the study found decomposition products, including CO2, C2H4, R 2 O, RF, OPF3, fluorinated phosphate, phosphoric acid and oligomers Fluorinated ethylene oxide. Author believes that the mechanism of the decomposition of electrolyte systems are due to the proton traces of impurities resulting fluorinated phosphate OPF2OR catalytic decomposition of the electrolyte. Gnanaraj [46] studied the use of the ARC and DSC 1M LiPF6/EC + DMC + DEC electrolyte system stability 40 ~ 350 ℃ temperature between 220 ℃ found, DEC and DMC was transesterification, 240 ℃ occurred during the EC reaction ring opening, 350 ℃ completely decomposed when the EC, the formation of a polymer. PA3191U-2BRS PA3191U-3BRS Reaction products are mainly in the condensed phase HOCH2CH2OH, FCH2CH2-OH, FCH2CH2F and polymers, derivatives are mainly PF5 gas, CO2, CH3F, CH3CH2F and H2O. Ravdel [47] comparative study of LiPF6 solid dialkyl carbonate and the thermal stability of the decomposition of LiF and found LiPF6 PF5, PF5 solution and the reaction of dialkyl carbonate, a series of products, including CO2, ether, fluorinated alkyl, and phosphate OPF3 fluorinated. Wang [48] on the LiPF6 kinetic behavior was studied according to the Arrhenius law and mass conservation to calculate the activation energy E = 104.2 kJ / mol, preexponential factor A = 1.12 x 107s-1.

Sloop [49] LiPF6/EC + DMC system at 85 ℃, decomposition occurs with PF5 and EC / DMC comparison between the reaction products of reaction and the reaction was found near the same phenomenon. LiPF6 decomposition products in the electrolyte in the first place PF5 and EC should be made to produce oligomers soluble and insoluble substances also generated phosphate. Lee [27] found that the breakdown products of PF5 LiPF6 Lewis is a strong acid, is a SEI film PF5 caused by the instability of the main reasons. Gnanaraj [50] a comparative study of LiPF3 (CF2CF3) 3 (LiFAP) LiPF6 and Lin (SO2CF2CF3) 2 (Libet) the thermal stability of the electrolyte and found that the stability of the order is: Libet> LiFAP> LiPF6. Hong [51] using the DSC study LiPF6 LiBF4 and lithium salt mixed electrolyte thermal stability. Li [52] that the PF5 is the source of the thermal decomposition of electrolyte, and adding a small amount (3 to 12%) of Lewis base additives and the formation of complex PF5 can significantly increase the thermal stability of electrolyte system, this study has been PA3191U-4BRS PA3284U-1BRS pyridine, and HMPA HMPN three Lewis base effects on electrolyte and found that significantly improved the stability of the electrolyte, and electrical conductivity of the loss was small (< 5%).

In general, at low temperature (<150 ℃), the thermal stability of the battery is mainly surface lithium anode, thermal stability and thermal stability of SEI film determined, and a higher temperature (> 150 ℃ ), the positive electrode material and electrolyte complex between the thermal runaway reaction is the main reason leading to the battery.

4 Prospects

Addition of flame retardants in the electrolyte, the electrolyte can suppress the combustion of lithium-ion batteries to improve the security of direct and effective. Research on the electrolyte Fireproof, the urgent need to solve the problem is to find new, low-cost flame retardants, so the electrolyte is non-combustible or flame retardant, without damaging or even to improve battery performance, its development has also considerable potential. In addition, the establishment of a high degree of confidence of the electrolyte flammability test standards, developing fire-retardant electrolyte lithium-ion battery will be a tremendous boost. Latitude E6400 battery Latitude E6500 battery

The thermal stability study of the lithium-ion depth, identify the causes of heat inside the battery, which, for a fundamental solution to its security is of great importance. This study is the use of calorimetry (DSC as the ARC, C80, etc.) to detect the heat generated in the battery case, but by the internal battery spectroscopy exothermic reaction took place to explore the mechanism is still in a virgin state, the use of new test methods overview of lithium-ion batteries are the root causes of thermal runaway, which is to solve the problem of key lithium-ion battery. Asus A32-F82 battery

1 Introduction

With an energy density of lithium-ion battery, high voltage, long service life, environmental pollution, etc., in electronic products, electric automotive, aerospace and other applications extremely important. However, in recent years the explosion of the lithium-ion batteries due to fire and even been reports of frequent safety of lithium-ionVGP-BPL5A VGP-BPS2 battery sparked widespread concern, while security is limited to batteries large-scale lithium-ion battery, the direction of high-energy bottleneck.

Lithium-ion batteries are the most important part of the material of the electrode and the electrolyte. Lithium-ion flammable organic solvent such as electrolyte, which is lithium-ion batteries are one of the great fire or explosion. After the destruction of the battery, organic solvents and steam can burn a fire or explosion. In addition, the security level of the lithium-ion battery electrode materials and electrolyte also include thermal stability, including in the normal discharge procedure, and even the abuse of non-normal conditions, the battery itself will not damage the thermal stability. This document from the combustion properties of the electrolyte and electrode materials and electrolyte thermal stability between the two in terms of lithium ion battery material safety advances in research.

2, the combustion properties of the electrolyte

On the combustion properties of the electrolyte mainly in two aspects: no flash point electrolyte retardant fluorinated solvent and flame. VGP-BPS2A VGP-BPS2B

2.1 No flash point solvent fluorinated

The lithium-ion batteries currently use carbonate as an electrolyte solvent, the linear carbonate can improve the battery capacity and charge-discharge cycle life, but their flash point lower at low temperature flashover, and fluorinated point more generally, even without flash flash point solvent, the use of fluorinated solvent electrolyte can suppress combustion. This study fluorinated solvent include fluorinated and fluorinated esters.

Arai [1] found that trifluoroacetic behalf of propylene carbonate (TFPC) and chlorinated ethylene carbonate (CLECs) can replace the linear carbonate in a better discharge capacity and cycle life. TFPC CLEC respectively, ethylene carbonate (EC), propylene carbonate (PC) composed of binary mixed solvents have higher flash point. But for CLECs / TFPC EC TFPC the conductivity of the electrolyte solvent are two weak, but CLEC / electrolyte TFPC basic life cycle showed good. Yamaki [2] two acetate methyl fluorides (AMF), two fluorinated ethyl acetate (EFA) and other fluorinated solvent esters found, with the anode electrolyte LiPF6/MFA lithium metal and cathode of coexistence have Li0.5CoO2 better thermal stability. Ihara [3] on the electrolyte 1M LiPF6/MFA study found that the system is available with an electrolyte M + DMC electrolyte LiPF6/EC movement comparable to the performance of the carbon anode with lithium VGP-BPS2C VGP-BPS5 intercalation of thermal stability better coexistence.

For solvents fluoroether found [4,5]: Fluoro methyl ether-butyl (CF3CF2CF2OCH3 MFE) and ethyl methyl carbonate (EMC) mixed solvent of flash point with increasing content MFE but in all fluorinated ethyl-butyl-ether (EFE) system and EMC solvent mixture, the flash point, but with increasing content EFE. In the MFE + EMC (4:1 vol) mixed solvent added 1M LiN (SO2C2F5) 2 (Libet) received no flash point electrolyte, and 1M + LiPF6/EC EMC electrolyte from the electrolyte to load LiCoO2 cathode discharge capacity without adverse effects, but charge and discharge capacity of the graphite anode decreased more. In the electrolyte by adding 0.1 million and 0.5 million LiPF6 EC, ambient temperature, graphite / LiCoO 2 battery all good performance cycle, 560 cycle, the discharge capacity can be maintained in the initial capacity more than 80%.

2.2 Retardant electrolyte

Retardant electrolyte is a function of the electrolyte, electrolyte flame retardant is typically added to the electrolyte by conventional flame retardant additives available. VGP-BPS5A VGP-BPS8

Wang et al [6,7] in trimethyl phosphate (TMP) as flame retardants to study the combustion properties of the electrolyte containing TMP and electrochemical stability, noted that TMP itself very good effects of flame retardants and stability to oxidation, but reduction of the graphite anode is less stable. They found that adding a total of TMP can inhibit the reduction of the decomposition of solvents, for example, in EC + PC + TMP (TMP <10%) and EC + Diethyl Carbonate (DEC) + TMP (TMP <25%) TMP ternary systems have better restore stability, but with increasing solvent content, the combustion of the electrolyte increase to amorphous carbon instead of graphite as the cathode, the reduction may improve stability of TMP. Ota [8] in 1m LiPF6/EC + DEC + TMP (6:02:02) system with 5% ethyl vinyl phosphate (EEP), the effective suppression of the decomposition of TMP, it is because that EEP ago conducive to the surface of the graphite anode of solid electrolyte interface (SEI) film formation. Yao [9] studied the trimethyl phosphite esters (TMPI) and trimethyl phosphate (TMP) on the role of the electrolyte and the electrochemical properties of the flame retardant effect was found for the same amount of TMPI and TMP, the former in improving the electrolyte resistance to the flame, while improving the electrochemical performance of cathode half GK479 FK890 GD761 cells, the authors believe that this is due to the effect TMPI on the stability of the surface due positive, and the flame retardant effect although the latter is better, but this resistance to the electrolyte burning effect is some loss of electrochemical performance for the price, the discharge capacity of the cathode half-cell loss was more severe.

Hyung [10] were used triphenyl phosphate (TPP) and tributyl phosphate (TBP) as a flame retardant found that even the addition of 1% (weight) of the TPP effect flame retardant important, burning rate transmission reduces significantly, Add 5% TPP can significantly improve the thermal stability of the electrolyte, and showed good electrochemical performance, while the electrolyte containing TBP cycle of poor performance. Wang [11] using 4 – isopropyl phenyl phosphate (IPPP) as a flame retardant for 1M + December LiPF6/EC (1:1 by weight) of the system, noted that fire is the best. The flame retardant mechanism IPPP gas which is carbon free radical mechanism and the mechanism of condensation complementary to each other KD476 TD347 C1295 work together.