| 1. |
- Gejke, Cecilia, 1973, et al.
(författare)
-
Lithium insertion in Sn-P and Sn-B-P oxide glasses
- 2000
-
Ingår i: Lithium Batteries. Proceedings of the International Symposium (Electrochemical Society Proceedings). - 0161-6374. ; 99-25, s. 144-149.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The behaviour of electrodes based on Sn2P2O7 and Sn2BPO6 glasses during cycling were characterized with diffuse IR reflectance. By removing the electrodes from the half-cells at different stages of the electrochemical cycling it was possible to follow the development of the glass structures during lithium insertion and extraction. It was found that the local network structure around the phosphate groups in the glass experience structural changes by the lithium insertion. These changes are not fully recovered by lithium extraction during the first cycle and are likely related to the initial irreversible loss of capacitance of the electrodes.
|
|
| 2. |
- Gejke, Cecilia, 1973, et al.
(författare)
-
Microscopic structure of tin-borate and tin-boratephosphate glasses
- 2003
-
Ingår i: Journal of Power Sources. - 0378-7753. ; 119-121, s. 576-580.
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of tin-borate and tin-borophosphate glasses has been examined with diffuse reflectance IR (DR-IR) and Raman spectroscopy. The basic network structure for these glasses is described as well as the positioning of tin in the network. Data suggests that the amount of phosphate present in the glass regulate the glass forming properties of tin. With borate as the dominating glass forming oxide, SnO acts like a glass former, but with increasing amount of phosphate SnO instead tends to behave as a network modifier.
|
|
| 3. |
- Gejke, Cecilia, 1973, et al.
(författare)
-
Structural investigation of the Li+ ion insertion/extraction mechanism in Sn-based composite oxide glasses
- 2001
-
Ingår i: Journal of Physics and Chemistry of Solids. - 0022-3697. ; 62, s. 1213-1218.
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of lithium insertion for two Sn-based composite oxide glasses, Sn2BPO6 and Sn2P2O7, was examined during the first electrochemical discharge/charge cycle. Electrodes based on these glasses were analysed with micro-Raman spectroscopy at different steps during the cycle. In-situ X-ray diffraction has been used to confirm the amorphous state during the lithium insertion and extraction process. No alloy formation between Li and Sn could be discerned throughout the first cycle. It was found that when lithium enters the electrode, a reaction at the surface of the glass particles takes place resulting in Li3PO4, Li2O and SnO2 formation. The charge compensation mechanism is thought to be the reduction of Sn2+ to Sn. The formation of Li3PO4 is found to be irreversible and is as such partly responsible for the large observed capacity loss during the first cycle.
|
|
| 4. |
- Gejke, Cecilia, 1973, et al.
(författare)
-
The effect of lithium insertion on the structure of tin oxide-based glasses
- 2001
-
Ingår i: Journal of Power Sources. - 0378-7753. ; 97-98, s. 226-228.
-
Tidskriftsartikel (refereegranskat)abstract
- Two different SnO-based glasses, Sn2B3O6.5 and Sn2B2AlO6.5, have been examd. with FT-IR and Raman spectroscopy at different stages during the first electrochemical cycle. Some disruption of the connection between borate units in the network occurred during cycling. There was also an irreversible formation of Li3BO3 that can be related to the large capacity loss.
|
|
| 5. |
- Gejke, Cecilia, 1973
(författare)
-
Tin-based Glasses: Structure and Electrochemical Properties
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents an investigation of microscopic structure and electrochemical properties, and their relationship, for various tin-based borate, phosphate and borophosphate glasses. Tin-based glasses have attracted a lot of scientific interest as anode materials in Li-ion batteries. The battery performance for a glass is promising, but the large capacity loss occurring during the first electrochemical cycle, is a negative feature. Furthermore, the mechanism for the lithium insertion and extraction process of the glasses is not well understood and it is a prerequisite for a rational optimisation of the properties of the materials. A cornerstone for the investigations is to understand the structure of the pristine glasses. Detailed structural characterisation of the complex glassy materials is, however, difficult because of the lack of long-range translational order. Various local molecular arrangements do exist and these have been probed using infrared and Raman spectroscopy. By combining this information with that obtained from neutron diffraction in conjunction with Reverse Monte Carlo modelling, a picture of the glass structures has been made on a length scale corresponding to molecular arrangements as chains and clusters. In glasses, tin is able to act both as a glass former and as a network modifier. Its function is dependent on the glass composition. The present structural studies show that, in a borate glass, tin acts similar as a glass former, whereas in a phosphate dominated glass, tin instead behaves more like a network modifier. In order to understand the mechanism of the lithiation process and the cause of the capacity loss, the structural changes of the glass materials that occur during electrochemical cycling have been probed using infrared, Raman and in situ Mössbauer spectroscopy. The results show that, during the first cycle, lithium reacts with the phosphate part of the network to form lithium orthophosphate. This is the irreversible process, which constitutes the major component of the capacity loss of the first cycle. However, in the absence of phosphate, the borate part of the network is attacked instead by the lithium but to a lesser extent. Thus, the structural role of tin influences the cycling performance, which is also dependent on the upper potential; tin and lithium form aggregates which lead to capacity fading on cycling above 0.8 V.
|
|
