Nail penetration test

The nail penetration test is very important and is considered to simulate an internal short in a cell. No electronic device can protect against an internal short, so the cell... 

Generally in a nail penetration test, an instantaneous internal short would result the moment the nail is tucked into the battery. Enormous heat is produced from current flow (double layer discharge and electrochemical reactions) in the circuit by the metal nail and electrodes. Contact area varies according to depth of penetration. The shallower the depth, the smaller the contact area and therefore the greater the local current density and heat pro-... 

Figure 12. Typical nail penetration behavior of a 18650 lithium-ion cell with shutdown separator. This test simulates internal short circuit of a cell. Key (a) cell passed nail penetration test (b) cell failed nail penetration test.

Figure 5.15. Impact fracture surface of C/SiC composites [24] (a) after Charpy impact test and (b) after the nails penetrated test...

Figure 20.16 shows the typical nail penetration behavior of a Li-Ion cell with shutdown separator. Clearly, there was a voltage drop from 4.2 to 0.0 V, instantaneously, as the nail penetrates through (when internal short circuit occur) and temperature rose. When the heating rate is low, the cell stops heating when the temperature is close to separator shutdown temperature as shown in Fig. 20.16a. If the heating rate is very high, then the cell continues to heat and fails the nail penetration test as shown in Fig. 20.16b. In this case, the separator shutdown is not fast enough to stop the cell from thermal runaway. Thus a separator only helps to avoid delayed failures in case of internal short circnit as simulated by nail and bar crush tests. Separators with high-temperature melt integrity and good shutdown feature (to avoid delayed failures) are needed to pass internal short-circuit tests.

Ichimura M (2007) The safety characteristics of lithium-ion batteries for mobile phones and the nail penetration test. In Proceedings of the 29th international telecommimications energy... 

FIGURE 18.11 (a) Comparison between thermocouple and IR-imaging temperature measurement for a nail penetration test. Temperature profiles measured using infrared imaging technique for (b) controlled a node-cathode short test and (c) control led anode-aluminum short test. (For color version, refer to the plate section.)... 

The initial temperature rise was lower for the nail test (137.5 °C) compared to the controlled anode-alnmimim short test (251.4 °C) for the same SOC condition. This is due to multiple-layer short and multiple kinds of short (including the anode-aluminum) that would have occurred during nail penetration. Based on infrared scanning for the entire cell [22], it was estimated that about 45% of the cell area showed 80 °C or above within 2 s of controlled anode-aluminum internal short while for the nail penetration test, it was only 15%. Chances of thermal runaway are more for a single-layer anode-aluminmn internal short than compared to a multilayer short incurred due to nail penetration. Anode-cathode short was foimd out to be much safer compared to anode-aluminum short as the cell showed a maximum temperature of 71 °C even after 30 s of continuous hard shorting. 

FIGURE 20.18 Voltage and thermal behavior on (a) heating test, (b) overcharging test, and (c) nail penetration test [27,34],... 

Due to their reactivity with electrolyte solutions, especially in the charged state, the most useful thermal behavior testing (e.g., DSC) of the candidate cathode materials occurs in the presence of electrolyte. Below, the results of a comprehensive study done by MacNeil et al. [9] have been used in preparation of graphs shown in Figs. 5.4, 5.5, 5.6, and 5.7, with several cathode/electrolyte system behavior trends identified and discussed common cathode name abbreviations used in the discussion are listed in Table 5.1. Similar studies are commonly done by the lithium-ion battery manufacturers on various cathode and/or electrolyte materials candidates and are usually treated as a basic introduction to the ARC testing and other safety-related experiments on larger cells (overcharge, nail penetration tests, etc.). 

In the nail penetration test, a lithium-ion ceU was mounted between two plates of similar heat capacity and naU was driven into the ceU while the ceU was fully charged (100 % SOC) in order to initiate an internal short-circuit. The test typically determines the heat flow immediately after the naU penetration. In this case, the temperature of the cell is monitored until the ambient value is reached (Fig. 5.18). 

Nail penetration For NanoBaseX, they showed superior performance in nail penetration tests of 10 AH cells of LiMn204/graphite cells, comparing a 20 pm PE/PP separator to 30 pm NanoBaseX. 

Several safety tests for batteries have been described (96). In the nail penetration test, a LiCo02/mesocarbon microbeads full battery with the branched oligomer showed a significant improvement in the thermal stability and was able to restrain the temperature of the battery at about 85°C. The nail penetration test was conducted according to the standard procedure described in UL1642 (97) and SBA GllOl (98). An internal short circuit occurs upon nail penetration, and the thermal runaway behavior can be observed if there is no mechanism to quench the heat or stop the chain reaction quickly. 

Matsushita Electric Industries Co. Ltd have described in patents [28] the use of a porous heat-resistant layer to provide increased abuse tolerance to hthium-ion cells. In particular, the presence of a heat-resistant layer provides improved performance in nail penetration tests. In one example, a heat resistant layer consisting of alumina particles and a polyacrylonitrile rubber binder is coated onto both sides of the negative electrode and used with a conventional separator. In one embodiment, the separator is not used, and instead the separation is provided entirely by the coating on the negative electrode. According to one patent disclosure [29], the battery does not need a conventional expensive separator sheet, thereby making the production cost low, which holds great industrial promise. ... 

Nail penetration test Mechanical abuse A nail penetrated through the battery causing internal short-circuit. Heat generated due to current flow through the battery and the nail. 

Video of nail penetration, which was performed to investigate the safety behavior of a cell under penetration of a strong nail into the cell, is shown in the results section of this article. Prior to the test, the cell was fully-charged at a rate of C/6. Once the desired state of charge was reached, the cell was carefully placed and safely fastened on to a specially designed stand. The thermocouple was placed behind the cell, which makes it not visible in the attached video. During the nail penetration test, the cell was perforated with nail and the position of the nail was... 

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